I've heard lots of problems from people who use WiFi printers. Personally, I'd stay away from them for that reason. However, there's something that a lot of people seem to forget or not know:
you don't need a wireless printer to print (or scan) wirelessly. You just need any (wired) networkable printer and a wired network to plug it into--and if that network also happens to do wireless, you can effectively print and scan "wirelessly" as well. So, for example, the Aiport Extreme Base Station would work for this, but so would any wireless router with a switch. You just need a spare jack to plug it into your network.
Basically any Ethernet-enabled printer should have a way to scan and print over the network connection. I have a Brother DCP-7056dn connected to my AEBS with Ethernet, and I can print and scan wirelessly via either Brother's software or Apple's provided applications (Preview, etc.). You just follow the standard procedure for adding the printer/scanner in System Preferences.
EDIT: I just looked at the most recent post (today) and the ones before that (February) and thought this was a recent thread, but since I forgot it's not 2012 anymore I guess my calculations were a bit off. Hope the OP figured this out already.
You can do the same with WiFi printers and scanners, but you'll often need special software. Most wired printers won't need this, and if you get one that supports standard langauges (PS/PCL, etc, rather than a computer-based driver-only language) you'll be significantly more futureproofed than if the you have the latter and the manufacturer decides to stop supporting it.
Of course, this just means that you'll need a wired network connection by the printer to plug it into. This is just my two cents, but I think you'll have a lot fewer problems doing this. If you have any particular printing or scanning needs (e.g., duplexing, color, etc.), I'm sure some people may have more specific recommendations.