802.11n, 5ghz
The couch in my living room is a bit of a WiFi black hole for me for some reason, which is unfortunate because it's also one of the places I most want to use it. The signal is weak, and occasionally disappears.
802.11n can run at 2.4ghz and be compatible with 802.11b/g, or can run at 5ghz without that compatibility. I tried flipping the base station over to 5ghz, and to my surprise, found that my connection from the couch is much faster and much more reliable.
The down side is the Wii and the PS3 both connect to the network using 802.11g, so I need to switch the base station back to 2.4ghz whenever I want to get online with one of those devices.
The killer is going to be when the iPhone 3G comes out in 24 days 2 hours 28 minutes (as of this writing), and I'm going to want my network at home to be 802.11g most of the time.
My best option may be to add another 802.11g network in the house for those devices and leave the 802.11n network at 5ghz. Seems like overkill, y'know?