We stayed at the Hotel Unius for 4 nights, arriving by train from the main Airport and walking the short distance through the park, past the Barbican and down Florianka to the hotel (250m). Don't bother with Taxi's from the train station as its really easy to find and takes no time to get there. Once we got to the hotel we where greeted by a friendly reception staff who gave us us the impression they had been stood their all morning just waiting for me and my partner to arrive. After a couple of minutes checking in we where given 2 room keys, a map of the city, a guide book and a pile of tourist information leaflets. After this we where escorted to our room (108) which was on the first floor in the corner of the hotel over looking the intersecting streets (see piccy). Our escort then subsequently gave us a tour of our room, showing us the how the safe worked, that the room had a ironing board and iron, how the tv worked, etc... even how the clock radio worked with its ipod/iphone dock worked. Even better was just as I went to my wallet to tip the man for bringing our bags up and giving us the run down of our room he politely bid us a good stay and left. Therefore leading me to think this level of service was the "norm" and not something the staff did to pick up some extra income. The room was impressive, modern decor, lcd tv (only 2 english channels though!) on the wall, big comfy bed, kettle with all usual drinks and a well stocked mini-bar. What was even more impressive was the bathroom, black sparkly marble, spots lights in ceiling, shower enclosure with big glass screen, heated floor and modern basin and tap with huge mirror fully covering the wall. The only negative I had about the room was the lack of bath but its only a minor point for me but would a issue for people who like having long hot baths on there hols. Also to note about the hotel is the free wi-fi which I clocked it about 2MB/s, not very fast but more than usable for checking the weather/news etc plus the other half checking facebook.....
The location of the hotel is ideal for exploring the city as the cloth hall, St Mary's, the Barbican and the main square are all within a 5 min walk and Wawel Castle, the Vistula and the Jewish quarter no more than 20 mins away. Transport links are all close with Krakow's main train station, tram stops and bus stops all within a short walk (inc bus 304, the bus to the Wieliczka Salt Mine, 40mins away). Loads of bars and restaurants around including one in the hotel. Can't comment on the one in hotel this as we never went in for either breakfast or dinner but looked good from the outside.
The only other point to mention based on the previous reviews is the noise from the street. I would be lying if I said there wasn't any however the room was fully double glazed with heavy curtains covering the windows leaving only the most drunken howls left to be heard. Personally I didn't have a problem with the noise and I think the room we had is probably the most exposed to the street. In the grand scheme of things it a very minor annoyance which should not put anyone off using this hotel as a base for there holiday as the location, the rooms and the service more than cover it.
Overall top notch hotel which I'd happily stay in again and recommend to anyone wanting to visit Krakow.