We stayed one night at Ibis Neukoelln hotel. If you are looking for a budget hotel in Berlin, this may be the good option.
Pros: the accomodation is comfortable and clean. Staff is friendly and helpful. Great breakfast. Great location, you can park your car in front of the hotel for free. The subway station is within 3 min walking distance, not 100% save though (once we met local bullies, but they spoke english a bit and we ended up with no harm done)
Cons: We got a smoking room (although none of us smokes), and room smelt of cigarette smoke a little. We couldn't change the room. Maybe when a was making my reservation I didn't notice smoking options. Be careful of that.
I had a bad experience with this hotel starting with the moment I wanted to get into the room - the card reader for one of the 2 rooms I reserved was broken and I could get into the room only after trying it more than 20 times. After going down at the reception and explaining what the problem is, the guy just put the card through the reader on his desk and sent me away. I finally managed to get into the room after multiple retries. Next day it didn't work at all - I was lucky I was noticed by the cleaning team. Thanks to those ladies I got a new room.
Otherwise, there was a girl at the reception looking always busy and upset, lots of noise coming from the bar across the street and not so nice area around the hotel.
Won't go there again. The reason I went there this time is they had a good offer of 55E for 2 nights over the weekend.