I have a 330xi and my friend has a 330i which I also drive in almost every day lol..They are both GREAT cars! The XI is heavier and you can't really feel
the "pull" since the power is going to all 4 wheels (biased to the rear) instead of just the 2 rear wheels but it certainly pulls especially from a full stop. You get all the reliability of a n52 engine + the speed you can't get in the lower end models. I have to admit I was looking into 335's the other day but they just aren't in my price range. I've gotten used to the power on mine (stock besides remus muffler, resonator delete, and K&N drop-in filter) especially after a year and a half but I appreciate it EVERY day even though all these newer cars are getting faster and faster with all their turbos..even the Japanese cars..but they still aren't a bimmer
As for the reliability.. I'm about to hit 88k miles and I've had it for a bout 8k miles. Around this many miles, your going to have to replace the head cover gasket which can run you about $4-500. Knock on wood that's the only major problem you run into other than regular maintenance which isn't too bad..you can reach 200k in a stride so I've heard and I don't doubt it at all.
As for mods...TONS of cosmetic mods but not enough for performance..I'm planning to rebuild my exhaust (catless headers, quads, mid-pipes), AA Stage 2 Tune, haven't decided on an intake (possible euro box), WEIGHT REDUCTION (especially if you decide to get an XI since they are 200lbs heavier than a regular 330i). You can really get up there with power depending on how deep your wallet is but there definitely is a limit for our N52's..there isn't much you can add with all the $ you put into it. But e90's all together can be lookers..real good lookers
Here's a link for performance mods:
Here's a link for how to get to 200k miles:
and for cosmetic mods just check out the Photo/Media Gallery and get some ideas.
You won't regret getting any 330 just make sure it has sports package AT LEAST. I have all 3 (cold, sport, and premium package) but if you have sports with the sport seats you'll be comfortable. And if you get an XI make sure you drop it asap!! That's all I got for you
Fuse 20 in the fuse box behind you glove compartment removes 4x4 for some fun..but you also lose ABS and traction control and your wipers go crazy til you restart the car and your blinkers too so it isn't safe to drive around with but good fun.