I have an '01 330i. Pretty much what is said above (I need to do the cooling system go-through though). I have replaced the water pump, but not the various hoses and expansion tank. I too had to do the window regulators. As noted above, you can DIY, about 1 hour per door is about right.
The other area to look at is the suspension. If the wheel shakes on braking at decent speed (50+), then it needs new control arm bushings. Easy fix, especially if you can get time on a lift.
The other thing to know is that when the shocks / struts go on these, I can imagine it being n not so obvious on a test drive. The car does not get "bouncy", instead, I'd say it gets "saggy". For example, it will bottom out on speed bumps. That too is a DIY job, but took me while. It was not clear to me how bad it was until I replaced them, and then I was like "woah" - so that is what the car drove like when I got it!
When I picked out my car, it was clear there was a significant performance difference between the 325 and 330. Same can be said for sport package. Premium package is nice, in that I do like the rain-sensing wipers.
I also respectfully disagree with the engine being devoid of character. It has character, it's just that it has the character that Greg describes. I think it pulls nice and smooth, power comes on in a very nice, even way. 330 has plenty of torque, and mine makes nice sounds. I guess this comes down to a personal preference. I don't like "buzzy" engines that feel like they are working hard all the time.
Another anecdotal comment about the 330i: My wife does not drive manual much. She had to drop me off in the car, and I saw about 1/2 the time she was starting off in 3rd (she is secretly afraid she'll throw it into reverse, go figure - so is timid about going too far left to go into 1st). She just thought it was hard to drive, had no idea she was in the wrong gear. The car will handle it!