To get the widest coverage, you need to wait for the 802.11n standard to be finalized. There's quite a bit of pre-n stuff out there. As long as you buy all your pre-n stuff from the same manufacturer, you shouldn't have problems. But you can't currently mix and match n class wireless yet as there is no official standard. n-class wireless is based on multiple antennas usually abreviated MIMO.
MIMO should improve the operation of b and g wireless too.
Linksys is pretty good as is NetGear and D-Link, though I'd rate Linksys and Netgear higher than D-Link.
Ideally, all the pre-n class gear should be flashable to upgrade to the finalized standard. Ask if there is such an upgrade path. I don't know if that's possible yet.
There is some risk involved in the purchase of pre-n equipment.
Phil