I've only been doing this for half an year, but I really sunk some time and resources into this. I'm fascinated by all this stuff especially the cryptoanalysis side of things and the antenna issues. I also realize there are quite a few bright people out there on this forum.
I started by using Backtrack 4 on a thumb drive and some of the wireless connections in my neighborhood as test targets.

I quickly found that using out of the box Orinoco Gold and Hawking HWUG1 adapters, i could barely capture the WPA handshake on my own router let alone my neighbors.

I built a 4 foot 12 db Antenna out of LMR 400 and I also tried a 30" Hawking Omni antenna. To this day, I've found out that unless my antenna is within close proximity (40 to 50 feet) on a cold night, I still cannot capture WPA handshakes good enough for Cowpatty. This denies me use of the Rainbow Tables. (Over the holidays, Christmas Decorations and displays offered me some clever locations for hiding that 4 foot antenna of mine.)

I have obtained quite a few Aircrack-ng quality handshakes which means I have to use JTR and Aircrack-ng for WPA cracking as my best resource. I am now working on these. I launched one at home last night with a 10 meg password file and got nothing.

Has anyone else had this problem with Cowpatty? It rejects a lot of WPA handshakes that Aircrack-ng accepts. I understand Aircrack-ng is faster but Cowpatty has some variations--one of which is the rainbow tables-- that seem to offer a broader and more elegant solution to cracking a WPA connection.