Depends which model you going for, 325i is pretty much bullet proof if previously looked after, 335i has the performance but pricey to maintain if out of service plan, also hard to find one which hasn't been modified in any way. I'd steer clear of the 320i, engine doesn't match the size of the car.
The seat belt handover mechanism sometimes plays up. The car is very low,
so parking where there is high kerbs becomes a challenge, so the front bumper gets scrapped a lot. PDC front and rear is a must, the rear glass is very slopped so rear vision is a challenge. Avoid black, it becomes a pain in the arse to maintain, I found myself polishing it twice a month to hide fine swirls and scratches. The best part of this car is the massive doors, they feel
so macho, like big arms, and the frameless windows. It is a pure 4 seater, not
sure if it has a third seat belt in the rear, and to sit in the middle is impossible as there is a plastic insert where someone could sit, same problem I have with the 125i as well, the car effectively becomes a 3 seater when you need to put a child car seat in. Chassis is amazing, handling is so planted, it just eats corners compared to the sedan, which I found awkward in extremely tight cornering situations. If I compare my 125i to the e92 325i, the 125i is more of a handful to drive in extreme cornering, the 325i probably being faster and more composed and flat.
My 325i was fairly reliable, it had 101 000kms on purchase, only thing that failed was a v-belt pulley and a dead battery, was traded-in on 141 000km. Be careful with panels, car is not local build so body panels have to be imported if damaged.