I know this topic is old...
But for hacking wifi I use Backtrack and an ALFA AWUS036H. NOT the N version or anything, but that specific model number. Can be had on Amazon or Ebay, just search out that model number.
This is the ONLY USB WIFI network adapter that I have had any luck with what so ever, unless the router or access point is within 20 feet or so. With this adapter and a 9dBi antenna I have had success cracking WEP nearly a half mile away.
This thing is powerful and sensitive, and the modified linux drivers are built in to Backtrack, all making it a plug and play solution. It can do packet injection, which is very important to having success at all.
Backtrack offers the "netbook remix" edition as well, and should perform fairly well.