Cracking WPA keys with GPUs

I first read the article and I thought wow thats a lot faster. Then I started doing some math and realized it's still not practical.

http://arstechnica.com/security/news/2008/10/company-puts-nvida-gpus-to-work-cracking-wireless-security.ars

They benchmarked a 8800GTX at 2,500 guesses per second. It's distributed software up to 256 GPUS.
2,500 x 256 = 640,000 a second

How many possibilities can a WPA pass phrase be? (I think my math is right)
Upper & Lower case possible characters. 26*2 = 52
Possible special characters like $@!%, at least what I counted on my laptop. 32
52+32 = 84
63 possible characters in a WPA psk.
A!/(A-N)! = 84!/(84-63)! = 6.486942682e+106
I took that really big number and divided it by (640,000 * 60 * 60 * 24 * 365)
3214056297949842159116168158203114584942029386406415805023892166920391523704839025459200000000 years to find all the possibilities
http://wiki.answers.com/Q/What_is_the_equation_to_determine_number_of_possible_lock_combinations

I did the same math and found how long it would take to generate all the possible combinations. It's amazing how much stronger a pass phrase becomes by adding another character.
1-5 characters would take 96 minutes
1-6 characters would take 5.2 days
1-7 characters would take 412 days
1-8 character would take 87 years

Site I've always used to generate keys.
http://www.kurtm.net/wpa-pskgen/

All in all I guess as long as you have a decent password your ok.