Joe Kissell at TidBITS has been documenting all of the problems with Mail in 10.9 while using a Gmail account:
I’m sorely tempted to look for a different email provider (something I was pondering anyway, for unrelated reasons), but it irks me that I should have to do so now just because Apple broke Mail in the very process of trying to improve the way it works with Gmail.
It’s pretty bad that Apple didn’t catch this in beta testing — it is, after all, a pretty big set of new bugs with the system’s email client when configured for one of the world’s most popular email services. That’s on Apple, fair and square.
But if you’re a Gmail user and expecting to wedge it into an IMAP client without ever hitting problems, that’s increasingly your problem.
Gmail is a highly proprietary, constantly changing, email-like product. It is not standard IMAP email, and it will never work flawlessly in standard IMAP clients. (It never has.) Google has always supported IMAP reluctantly and poorly, and that won’t change — in fact, it wouldn’t surprise me if they removed IMAP support in the next few years.
Gmail’s primary, most important, and best-supported client will always be its web interface, with its own native mobile apps following. Everything else — especially standard IMAP clients — is a less-profitable nuisance to Google, not showing ads and holding back feature development by not being under Google’s complete control.
If you want to use email in a browser and Google’s mobile apps, use Gmail. But if you want to use standard IMAP email apps, use a standard IMAP email host.
Update: Joe decided to leave Gmail because he wanted standard IMAP structure and behavior. Good move, for the right reasons.