I recommend the Cisco 1231 as well.
We use the 1220 (the earlier B model) in a high-rise building with lots of steel, lots of flourescent lights, and lots of concrete. We can make it up about 4 floors with an 350-series card...the signal quality is better though with a lot of these integrated wireless solutions in laptops, especially if it's running a broadcom chipset. The signal quality isnt excellent 4 floors up, its a little bit below halfway on the strength bar. The "Excellent" signal drops off after we go two floors up. This is all using the standard rubber duckies they send with the unit.
I've seen the 1231 in action in a similar environment, with similar results. It's definitely good stuff.
I have also setup a 1220-based network in a huge (probably 9000sq ft) 3-story house. We had to use two AP's there, but not because the signal wouldnt reach all the floors, it was because the kitchen and the laundry room were in the LOS from the AP to a certain section of the house, and whenever the washers/dryers (yes, plural...this man had many children) would turn on it was like a brick wall going up in front of the signal and it would just die. We had to install a second AP closer to this section of the house so the signal was strong enough to penetrate. Just something for you to keep in mind. It ended up working out better in the end because when we redesigned the placement positions of the AP's, we covered more area outside the house...which the homeowner took advantage of in the form of a laptop, a lawn chair, and a lot of beer. He was pretty satisfied.