Yes... Gmail sync'ed to my Android tablet and smartphone, both usually on wifi when I'm at home or at work. Most times there isn't a problem, but there have been a few instances where an email I know I sent never arrived, and wasn't anywhere in my history (sent, drafts, outbound queue, etc.) Neither I nor my geeks (one of whom is a 'droid savant) have been able to figure out why.

It doesn't help that the technology gods and I don't get along.