Have also stayed at Gat Point Charlie – about 6/7 years ago. And like Bolt says – nice rooms, good location (located about 2mins walk from the former Check Point Charlie (as you might guess from the name)
We also enjoyed the cocktail happy hour 🙂
Located close to the station for the U2 and U6 lines. The Visit Berlin tourist card that you can buy gets you unlimited travel on the U-bahn, S-Bahn, Buses and Trams plus entry/discounted entry to museums and discounts at restaurants. found we basically recovered the cost of the 3 day pass while we were there.
Visit to the roof of the Reichstag is free, but if you pre-book your time slot now you can bypass the queues on the day (if you want to wait till your there, then you have to queue at the visitor centre to get your passport checked and get a timeslot for later that day (at min at least 2hrs later but upto 2 days later, so prebooking is a lot easier)