Car audio in it is a fucking joke(Even if it has harmon kardon option), even E38 audio system is a joke.
Most of petrols are a fucking lumps, heavy and very very slow for the amount of petrol they guzzle.
Only 3.0 and 2.8 are worth of looking at, 3.0 had problems with piston rings so if it wasn't done it might burn a bit of oil.
Other than that those petrol motors are bulletproof and can do thousand of miles.
Those cars have been used hard through their lives so check for obvious stuff, also check rear subframe since those rust to hell.
SMG is okay if serviced well, still nowhere life expectancy of conventional Autos,
and keep in mind that those are shit at low speeds and some local od school gearbox mechanics might not have clue how to fix them.
Manuals will be most abused cars, if you want you can put M3 diff into it, but you will need also m3 rear subframe for that keep in mind M3 diff is shorter.
Diesels are much more of maintenance worry, head gaskets, turbos, injectors those are biggest worries of those,
also would forget those seem to always burst some cooling pipes or have small leaks, and always have air in cooling system (Both petrol diesel).
Coupe is as long as sedan, sedan looks like shit tho, coupe has more space in front and can sit 2 adults in rear however not that comfortable in longer journeys.
Look at front struts for any deformations those are seriously weak and especially if it had custom hard suspension can bend or even break under stress.
Sunroofs can leak and sunroof seals cost shit ton of money and most likely won't fix leaking problem lol, also if sunroof system is broken then it is such a shitjob to fix it...
-Not that fast
-Consumes lot of gas for its power
-Pretty okay driving feel
-Good car for DIY mechanic except few things
-Pretty fatty compared to E36
-Most of them had rough life and are in rough condition
-Audio system is huge pile of crap
-Very meh as SPORT car in stock form