Affordable luxury
Here's luxury hotel that's not stuck up. The staff is formal but not stiff, and there are some "bus tour groups" among the guests. The rooms are large, well air-conditioned, and extremely well sound-proofed. This is a good splurge choice for comfort and convenient location (West side, Charlottenburg-Kurfürstendamm-Kaiser Wilhelm Memorial Church area).
You'll never run out of hot water here! They have a pillow-choice menu, huge bathrooms, an indoor pool, and a massive buffet breakfast. But extra costs can mount up if you don't plan for them.
You can get a lower rate by booking well in advance, and using the hotel's own internet site. Try to get a rate that includes taxes and breakfast (if you care about big breakfasts, or don't want to go up the street), because the un-included breakfast is likely to be 25 Euros per person.
The concierges are friendly and helpful, and didn't hint for a tip when giving minor advice. Nearby transit stops are (in order of close-ness) Uhlandstrasse, Kurfürstendamm, Zoolologischer Garten, Savigny-Platz. The #109 bus to the airport stops one block away. (This is a standard bus line, 2.10 Euros=Zone AB single transit fare, not the special airport run.)