I remember something like this on MacOSHints. However, many user comments tended to think that if many people start doing this it will risk gmail becoming a paid service or something, as they will lose advertising revenue.
I don't mind checking gmail in a browser, it has such nice little features (i.e. keyboard shortcuts) and is so much faster than other webmails. I've also set check gmail to an F key using Butler - with one press of a button I can check my mail now, pretty cool I think. Of course you don't have a copy of messages saved on your hard drive, but like manofsteel said, you could always forward them.