I use Googlemail a lot. Mostly out of the genious Web Interface, but sometimes I tend to use the Mail.app that comes with MacOSX. There is some trouble going on with configuring Mail.app right, that there are no dublicates of your messages. But its not that hard.
What I painfully found out today was, that if you chance the language of your Gmail Webinterface … well don’t.
I used the german Interface, but I had to change the language to english because a plugin I needed was only availlable in english. What Gmail does when you change the language of your interface is to change the names of all Labes / IMAP Folders in the background. So my “Alle Nachrichten” folder got renamed to “All messages” which screwed up my Mail.app and I had to resync the whole Account – which takes about three hours with my 30.000 + Messages.
It seems although as if there is no data corruption – only the need to resync everything.