Sorry, I don't check e-mail much on the weekend, but happy to pipe in here.
Yep, used to be an NSX owner (miss it, ask my brother) and contimplate getting another one all the time. Anyhow, let me try to answer some of your questions, I have a 2001 and have had it for three years, which is about the same amount of time I had the NSX, so I can speak definatively about both cars.
Yep, m5board.com is where I go and I believe has the best information and mature discussions, very reminiscent of Prime. You should do a search there and you will find many discussions on this very M5 vs. NSX topic. OK, my opinions:
the Good:
396hp
TORQUE everywhere
Great build quality
Five passengers at speed
Stable E39 platform
Real six speed (no SMG)
No Bangle butt
CPO includes up to 100,000 maintenance (includes all but rubber and gas)
396 hp
the Bad:
4000+ pounds
Understeers without camber plates (Dinan)
Weak clutch
Tires last <10,000 miles (NSX folks are used to this already)
Small-ish E39 trunk (multiple golf club bag challenged)
No spare tire
Uninspiring stock exhaust note
BMW brake dust (OK nitpicking here)
Scared to death when my warranty runs out (never a concern with the NSX)
4000+ pounds :frown:
Things to watch out for:
CPO cars are worth wild, the coverage goes to 100,000 miles or six years
VANOS has been known to be an issue with earlier cars
ALWAYS check to see maintenance history
Careful of M5's from the factory M5Driving Experience, they've been beat on
Headaches of owning a German car? YES. I have been fortunate that I haven't had any real problems, but for a while there, it seemed like my SES (Service Engine Soon) light was always on. It was always something small and covered by warranty,just a sensor or something, but it's annoying going to the dealer. My NSX was only in the shop for wear items, I wish I could say the same about the M5.
Bottom line, I need a four door and have only a two car garage (wife gets the other slot) and I'm not keen on having a decent car sitting outside all the time. The M5 is the only serious contender in this category and I don't regret the decision. As mentioned, I miss the NSX, but for my need it isn't an only car option, a possible supplement for me, but not a replacement.
Hope this helps, if you have any specific questions, I will try to remember to check back, Kevin