As I reported a few months back, I noticed an uptick on dropped calls and overall poorer performance when I upgraded from 2.x to 3.0. Basically it felt like the phone reverted to the same performance levels before the 2.1 upgrade. So I hoped it was a simple visioning error and the 3.0.1 would take care of it. No such luck. Seems people with 3.0.1 are having the same issues as those with 3.0. So now I guess we have to wait till 3.1 for a fix. What really bothers me is that people with the 3Gs that came from the 3G have experienced the same problem in reduced performance. I guess buying the new 3Gs is not going to help.
Here is a link to an article I wrote for iphoneLife giving tips on reducing dropped calls. Although it was written for 2.0, its still relevant today.