I too have noticed this OS crashing when using wifi at testmyiphone as well as the iphone test at dslr.com. I do see, when it does not crash the iphone, speeds up to 6 Mb/sec.
The thing that bothers me is that a search say at howardforums.com in the iphone forum does not bring up others having the same problem. I do see a post on the same problem on the macintouch forum.
After every firmware update (up to and including 2.2) I have done a full restore, my phone is not jailbroken and I only have a few apps.