current '04 330ci ZHP (m-tech 2) owner for 2 years
174,000 miles, still drives great, still love my commute, still get compliments.
Previous owners neglected it a bit, had to replace:
rear subframe bushings
DISA valve (common)
VANOS unit (common)
Valve cover gasket (common)
Crankcase Vent Valve (sorta common)
various cosmetic parts (easy)
previous owner probably replaced cooling system and MAF (Mass airflow sensor)
If you have a decent income, it's worth the maintenance bills. I'm still in love with it 2 years in.
Pay no attention to these edgelords, if it's what you want it will be worth your time and money.
Just make sure the cooling system and VANOS unit is good.
If you haven't picked a specific car, try to get a ZHP. It's 2/3 of an M3 for 1/3 the cost. Its one of the all time great DD's and IMO looks more timeless.