It's in the news. I'm tired of the drop calls when switching. Hopefully at&t and apple will do something about it soon.
http://www.freep.com/apps/pbcs.dll/article?AID=/20080725/BLOG01/80725030/1001/NE WS
Below is copy and paste from the link above
"Although I've had a relatively glitch-free experience, lots of other users around the country have complained of frequent AT&T network outages, dropped calls and sometimes slower-than-molasses connectivity. Probably some of that can be explained by the fact that, says AT&T, sales of the new 3G iPhone have been double of what they were when the first version of the phone was introduced last summer.
AT&T denies any widespread issues on connectivity. But there are hundreds of posts - 874 as of this morning - on one of Apple's iPhone 3G discussion groups (
http://discussions.apple.com/) discussing intermittent 3G connectivity and frequent but short "no service" messages."