Great advice Vader, maintenance is always super crucial with BMW's, especially the cooling systems, keep an eye on that fan and thermostat housing. As long as your on top of proper maintenance the cars are always a joy to drive.
I have 18x8.5 on my e36 and mine wont rub under hard cornering or while autocrossing, but like Vader said i have rolled my fenders ever so slightly. Its not really difficult to do with the right equipment..
I actually really like the way 17's look on these cars too but it basically all comes down to how much you lower the car and the tire size you go with.