I know people would instantly say "yes" right off the bat... but it really all depends on what you're looking for. The slight differences in body style aren't worth the extra cash, and in my opinion the performance isn't necessarily worth the cash by itself either. The advantage of a 330 is that you can push the car close to its limits, and you're not breaking the law (too badly). The M3, on the other hand, is basically a street-legal race car. You really can't push it to its limits without doing something which would get you a pretty crappy ticket (or arrested). Is it fun? Yeah, its incredible... blows my mind everytime I drive it. It's worth the extra money TO ME, because the styling, performance, and most importantly the feeling I get when I drive it, all add up together to make it worth the extra cash (and A LOT of it at that).
Just keep in mind... I'm paying almost twice for the M3 what I paid for the 330 (but that includes the upgraded service packages and some extras). It's not "just a little extra"... oh, but to be honest, the insurance hit is negligible, at least with my company.