The hotel is excellent. The lounge was open 7 days each time I've stayed there. The Health Club is the best hotel health club that I've stayed at, cost for hotel guests is 10 euros.
Could ask for a castle view - its excellent. The hotel is a 5 minute walk from the nearest tram and nearest subway station (though the two are on different streets) - your about a 20 minutes walk from the Charles Bridge. Every experience I've had here has been good. One other item - if your travelling for pleasure - take the white vans from one of the ground transportion vendors to the hotel - i think they charge 360 crowns per destination - a cab will be 650-700 crowns. Its usually best to take a cab back to the airport (especially in the morning) but no need to pay double coming in - I actually like it when they have 2-3 stops as inevitably they'll stop at the Hilton last as its on the road back out of town - you'll get a free 15-20 minute mini tour of downtown Prague!!
Enjoy