[Flow]

I've used Mail.app for my Gmail since Tiger and even now on 10.9 it works just as well.

It's unfortunate some people have problems, but even if it may seem so, they don't speak for all 10.9 users.

Hope your problems gets fixed soon.

[nikoftime]

I'm interested to know - before the 10.9 upgrade, did you have "All Mail" visible in IMAP in your Gmail label settings?

Also, about how many messages did you have in the inbox that worked?

[Flow]

I don't use "All Mail", I just use the "Inbox" at the top of the sidebar.