i switched to google apps for mail (and calendar) some time ago. i use thunderbird on both linux and windows on both my desktop and my laptop, and connecting them via imap to gmail servers works a lot better than having each of them download mail through pop and use the same mailbox files on a shared folder. then when i got an iphone i was able to easily work that in as well.
maybe i could have done imap without going to google, but i am also able to sync my google contacts between all my thunderbird installations and my phone, which is another bonus.
all in all it's been a good move for me! i even imported all my existing mail from my computer into google without significant issue. don't remember how i did that exactly, but if i was going to do it again i would do it all through thunderbird by just dragging the messages from my local mail folders to the gmail imap folders.
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