Touristy? - YES! Actually the only reason for it to be named Isla del Sol is to attract tourists and yes, as you can imagine its very touristy and yes, the locals take well advantage of all the visitors (more about hidden costs below).
From Copacabana, Isla del Sol appears to be "THE" thing to see and I agree, however Copacabana is a very nice little town - much nicer then Puno I would say, so if I could do it otherwise I would have stayed longer here (you can do Perusian floating islands from Copacabana) instead of Puno.
So, how do you get to Isla del Sol? There are at least 4 different boat companies, two of them operate from the dock and the other two are sold through agencies. The agencies will try to tell you that only one company operates and that's its always sold out, but don't get fooled - they will also forget to tell to that your trip will be twice as much. It seems that the boat prices are fixed, so I booked with the agency. (if you have other price information, please email me). To see the island, you have following options:
1. Day trip. Boat ticket for the day trip (which is the most popular thing to do) is b.35, which seems cheap, but unfortunately trips final price will be almost double (b.65), due to hidden fees along the way.
The boats will leave 8:30am from the dock and arrive at the North side of the island 2 hours later. Boats are slow, but ok comply - all 4 companies are pretty much the same. From pier North you have two options:
1.1 see the attractions and return to the pier North no later than 1:30pm in order to get the boat that will take you to South part of the island, there you can see the attractions until 3:30pm- the departure time of boat back to Copacabana. Additional expenses: attractions North b.10 + attractions South b.5 = b.15. Total of: b.50.
1.2 see the attractions and afterwards walk to South part of the island where the boat will be waiting for you to leave at you 3:30pm back to Copacabana. Additional expenses: attractions North b.10 + entrance fee to path from North to South b.15 + attractions South b.5 = b. 30 making the total cost of the trip b.65.
Not including b.2 that locals ask from you every time you take a picture of their lama or them.
I will recommend 1.2 simply because the main attraction is certainty not the museum, the little (un impressive) ruin or the stabled rocks. The main attraction is the TRAIL! It's gorgeous. The trail is approximately 11km and it may sound intimidating, but its really not. It does go up and down and with the altitude, you'll certainly feel it, but it's not really challenging at any points. If you are fast it will take you 3H, if you take your time 4-4.5H.
2. Half day tour. Leaves at 8:30am and at 1:30pm, coming back at 12:30pm and 5:30pm. With 2h sailing out and back, you'll barely have any time to see enjoy the island. Also, the tour only goes to South part of the island. I wouldn't recommend this trip and assess it as waste of time.
3. Out one day, sleep on the island. You have opportunity to buy one way ticket and stay on the island. You choose if you want to go to North or South for b.25, the ticket back is b.20 (however they might charge more).
If you choose to stay, you can use a day to visit Isla de la Luna, which is approximately 1H boat ride. Isla de la Luna is virgin and don't really have anything but beautiful nature. Since you can't stay there, you would normally go for couple of hours. Boat prices to go to Isla de la Luna are much more unofficial and I have heard people being charged anything from b.15 to b.200 (which I believe must have been private shuttle).
North vs. South?!
North side is less populated and the houses are spread out much more. It feels much more virgin and there are several beautiful beaches. There are hostels and hotels, some of them at the pier, some on top of the hill with gorgeous view of the lake and snow covered mountains (on a clear day) and some right on the beach. Also, since there were many tents on the beach, i assume camping is an option.
South is more of a village and is mainly located on the hill, (read. no beach) much more populated and offers lots of restaurants and mini stores. It has many places to stay, which makes it a cheaper option. There might be a tiny beach somewhere, but I haven't seen it.
I loved the island, it's beautiful - the trail is great! I could imagine that a night at North side would be very nice and peaceful and can only imagine how stunning the sunset would be.
I do hate, that the additional costs are not just included in the ticket price, or that the agencies don't inform you about them. It's a matter of expectations, really. If the tour costed b.65 I would still have done it and would have been a much happier client today, instead of getting x3 unexpected (unpleasant) surprises.