Stayed one week as a family with two older children.
We were looking for a place to relax and unwind for a week, hence chose the Parco Smeraldo. The hotel will arrange transfer from Naples Airport that is not particularly cheap but is efficient and ensure a fairly seamless transfer with taxis either end and either a fast boat or a hydrofoil.
I have been to Ischia before: unlike Capri it's a genuine 'working' island with lots of green (including extinct volcano) and predominantly domestic visitors (and loads of Germans but very few Brits and Americans). Most of the hotels are from the 70s and 80s and it's not a high-end destination: fortunately no plasma tvs. Food is a lot better than Capri though and it has some (not great but decent) beaches - including Maronti where PS hotel is. That said, sea is not very clean so we used the pool.
PS is quaintly old-fashioned which is part of its charm. Yes it could do with a spruce-up but I don't think most of its guests care much. We found it to be a high 3*/low 4* standard and perfectly adequate for our needs.
We stayed in one of their apartments - a separate building at the far end of the beach and an easy 5 min walk from the hotel. Our apartment had 4 beds on two floors and a large lounge and bathroom: not luxurious (TV dodgy and furniture old-ish) but perfectly fine. Impeccably clean. This building has 8 apartments with a private terrace area which is essentially never used. The only issue we had with location was the day it rained but reception sent some umbrellas round.
It should be said that Maronti beach suffered a lot of damage in 2009 and is smaller that it used to be at the hotel end: this is being rectified as a wall is being built to limit damage in the future.
We were on a half-board basis. Breakfast was OK (usual in Italy) and plentiful. Dinner/lunch was really quite good with an excellent vegetable buffet and a choice of 3 starters and 2 main courses. We found it was not quite as good in the last couple of days when hotel was 100% full but service was polite and flawless throughout. Nice bright dining room, lovely tiled floor.
Evenings are quiet but that suited us. Family that runs PS owns a small tour operator too and plenty of excursions are available. Wi-Fi in hotel lounge only.
Pool is not large but lovely at 30c: we all enjoyed it although probably not great in high summer. Internal pool complex was fun too. We did not use any of the numerous treatment facilities. Can we recommend the hairdresser (available 3 days a week): Lucia uses blades more than scissors (a' la Bumble and Bumble) and is really good. Cheaper and better than the rubbish available in London.
Customers were a mix of German and italian: some were elderly but we knew this and it was of no concern.
We would not stay longer than a week but it was good fun and would recommend. If you want noise, plasma tvs and expnsive restaurants then go the the Amalfi Coast.
Two more things: beach restaurant next to hotel (ida - see their website) was excellent. Also, there is no trailer park next to hotel: it's a small camping site with some funky motorhomes from Germany. It was no issue whatsoever (no noise, no smells etc).
If you feel like a splurge, best restaurant on the island is at Forio (Umberto a mare): 40 mins or so by car but thoroughly recommended.

if you are looking for a 4 stars and a really nice hotel with all the conveniences forget it
its a familly run hotel
it is on the beach yes ;;; next to a mobile home park
there is nothibng to do
the room are not very big, tiny bath tub
just shampoo and shower gel no Q tips no hair conditionner

vintage tv so small black and white must come from one of the trailers,its vintage

hotel is gloomy and the atmosphere is geriatric, and i am not spring chicken either but its depressing no internet, hardly anything in the mini bar
price way too much i paid 173 euros with dinner and breakfast which i a complete rip off

quickly left for sorrento and stayed in a lovely 4 statrs hotel that i knew with 5 stars service and paid 150 euros with breakfast, with fabulous buffet breakfast; 24 hrs services, flat screen tv, fully stocked minibar, in a quiet location, yet in town, with pool ( and pool service ) and private beach

i you are going to ichia look carefully before booking a lot of hotels are old

The service in Parco Smeraldo is more than excellent.
The hotel itself is rather simple, but the territory near the hotel is really beautiful ,as well as the beach and the view from the above.
Spa - great.
Food - excellent.
The best place for relaxation.
But if you prefer activity, it's not the right place for you.

We stayed at the Parco Smeraldo for 3 nights in early Sept. We opted for Ischia, after 4 nights of playing tourist in Rome, given the reports that it is more laid back and less crowded than Capri and we needed a few days of relaxation in the middle of our Italy trip.
We picked this hotel based on Trip Advisor reviews and because of it's beachfront location on Maronti Beach. It worked out well as a place to kick back after the torrid pace we set in Rome.
The accomodations were fine in our beachfront room with its patio overlooking the beach. As others have noted, the Hotel and Spa is quite popular with German tourists and Italians looking to get away for a few days. We did not meet any English speaking guests while we were there and most of the staff is rather limited in their English. This, however, was not a problem and we were able to get by with our limited knowledge of Italian. I would not let this factor deter anyone from staying there if what they offer is what you're seeking and what they offer is nice accomodations in a beachfront location.
A few general comments about the hotel:
The Beach: Certainly a nice long beach with a private area for hotel guests with an ample number of beach lounges. The Med. waters were quite refreshing given the quite warm weather we encountered. The one drawback about the beach was it sloped quickly to the sea and, while not at all dangerous to swim in, it was somewhat difficult for me to get out of easily given the fact that I have a couple of shoddy knees.
The Pool: It is located in a prime spot overlooking the beach and is quite large with a couple of water jets located along its sides. The pool is fed by warm mineral waters from the thermal spring and Spa. Consequently, the pool water temperature is very warm. For those who enjoy warm pool water it is perfect to sooth weary bones. Personally, given the warm weather we had, I would have preferred the water a little cooler in order to be a little more refreshing.
The Accomodations: Our room was of good size, clean and comfortable with good air conditioning. The AC was a welcome feature. Like all of the beds we experienced while in Italy, it was firmer than we are used to and consisted of two single beds pushed together to make a queen. It was, however, comfortable enough. The hotel has a lovely, sizable porch overlooking the pool and sea and was a nice spot for sipping an espresso or cocktail.
The Spa: It was well appointed and their special services such as massages, manicures, facials etc. were quite reasonably priced.
The Food: Given the location of the hotel, we chose the option of having 2 meals a day at the hotel. In my opinion, the food was just OK. We did discover that there were a couple of small beachfront restaurants just in front of the hotel. Both were reasonably priced and served great food. While not offering huge menus or formal dining, their pastas, pizzas and fresh fish meals were a treat. In hindsight we would have been better off not to do the meal plan at the hotel but rather have some meals in the hotel and others at the cheaper beachfront spots.

All in all, we enjoyed our stay at the Parco Smeraldo and the Ischia experience. It was a nice, short respite from our active tourist mode.