According to theappleblog, some* older iPhone and iPod touch users are having some issues with the 2.2.1 upgrade. Apple's forums are lighting up with people whose Wifi has been adversely affected by the update. According to the blog, Apple is reccomending a hardware replacement and that the replacements NOT have firmware 2.2.1. That would imply that there is no easy way to reverse whatever damage 2.2.1 hath wroght.
Anyone out there have first hand experience with this kind of problem? If for some reason, you haven't upgraded to 2.2.1, you might want to hold out for a minute.
