For the OP:
Coming from someone who is a BMW fanatic.
The E60 has the wonderful S85B50 engine-5.0 liter V10 Multi-port fuel injected, 10 throttle bodies, quasi dry-sump oiling system, etc et al.
Buy one that has had the recommended maintaince schedule followed (I.e. Valve adjustments every 30k or so, and 5-7.5k oil changes with castrol tws 10W60) and the engine will be darn near bullet proof.
The body and paint are great on BMW's no need to cover it
Interior has great fit and finish, BUT if you ever need to take it apart for whatever reason it is a royal pain to get back together so that it never squeaks or rattles because of the tight tolerances.
Brakes are okay for the first stop or two but quickly fade away, I would honestly upgrade to some stop tech if you plan to ever go to the track or anything else with it with some regularity, or if you are a semi-talented driver. Also don't be surprised at 700-800 bucks just to the fronts yourself. The brakes on these are over-priced for how underwhelming they are.
Suspension is amazing stock, but around 80-100k the struts and shocks will need to be replaced, and likely all ruber bushings in the suspension. Unlike American cars where the rubber seems to last forever on BMW they wear out, and once worn you can tell a huge difference in handling (when worn out the steering feel becomes almost like that of a SHO). Not to say that SHOs don't handle well because they do indeed amaze me, but the steering feedback just isn't there like a BMW.
MOST IMPORTANT
DO NOT GET THE DCT transmission. They are fun and amazingly fast, but they eat clutches and flywheels every 30k or so. And if the hydraulic pump ever goes, you're out several grand for it. YOU MUST GET THE MANUAL!!! A well maintained manual tranny M5 will last you a life time.
Lastly preventive I've maintaince is imperative on BMW's if you do not fix that stupid $10 part it will destroy a 3k part. It's not like most american cars where you can just neglect them and they continue to run for 100k until the finally blow. Conversely take care of it, and at 200k you will only think it had 50k on it. The same cannot be said for most other (well maintained) high mileage cars. They will still give away their age somewhat.
