Claiming itself an "airport hotel" is misleading. Even distance wise is closer to TXL, it still took 30 minutes to get to the airport by bus or roughly 20 Euro by taxi. With a little extra(10-20%) time or taxi fare, I could have stayed in any other hotels in downtown with a comparable hotel price and with much better facilities and surroundings and yet, I didn't have to make this extra trip to move to this hotel a day before my flight.
I tried to make a change/swap to stay in IBIS Berlin Messe to save a trip to travel to this hotel, but was rejected as they claimed I already paid the hotel. This is totally not acceptable from a customer's view, after an 5-hour bus ride from Prague and got off at ZOB where IBIS Messe is located.
Even if you need to catch an early flight and willing to pay 10~20% extra taxi fare, I would suggest to stay in any other hotels in downtown and enjoy your last night in Berlin rather than moving to this hotel to catch your flight at TXL.