My AT&T cellphone has been dropping calls and getting bad connects for a couple weeks now…since about the time Cingular became AT&T. Based on the experiences of others down at the Comic-Con, I'd say it's not just me. It wasn't this bad before.
If you have a GMail account, you might want to check your Spam folder carefully. Their filters are declaring an awful lot of legit e-mail as Spam, at least on my accounts. Unfortunately, there seems to be no way to turn it off or adjust its sensitivity. I guess you really do get what you pay for.