I just bought a '06 E46 M3 before Christmas and I love it. This car has the same engine as the M Coupe you're looking at so I can probably throw some info at you based on the extensive research I did before my purchase (you can still find my post here on Prime asking for advice).
- I don't know where the negative engine info is coming from in some of the posts but from what I've found gathered, M engines are far more reliable than regular Bimmers. The failures of the VANOS system are commonly mentioned in M forums but these tend to be isolated to earlier models and were fixed by BMW for free after some class action thing. As with all car forums in the world, you only hear of bad crap that happens but you never see posts where someone just says their VANOS is awesome or how they are amazed by the quality of the snap ring in the NSX. In reality, failures are very rare. The early M3s had an issue with the rear subframe tearing up, which was permanently fixed with the 03 model, this was also an issue that didn't affect a large number of cars. Some SMG trannies had occasional pump problems but I got a 6sp so I didn't worry.
The E46 M3 owners I've met and spoken to have not reported any problems, one of them has an 01 with 13K miles, the other is a 03 with 110K
A lot of it depends on how the car was treated and maintained by the previous owner(s), just like the NSX. If you find a prime example like I did, a worry free ownership is almost guaranteed.
- Maintenance cost is not that bad. It's more than a "normal" car but this is also more of a car than a Camry or an Accord. Oil change is ~$200 every 15K miles but it's easy to do yourself so if you own a garage you shouldn't have a reason to pay for this. There are two inspections to be done appropriately named Inspection I and Inspection II. They are done once every two years and they alternate. They include all the fluids and stuff, but Inspection II also ads valve adjustments and couple of other things. My local dealer charges $1200 for I and $1800 for II. This is also all stuff that can be done at home, although you do need to invest in a couple of special tools, totaling about $200 or so on Amazon. You can also do the brakes on these cars pretty easily.
In the first two months, my M is ages more reliable than my Subaru Impreza was, although at 123K the Subie had more than twice the miles when I got it. The fun factor (on dry, paved roads) is unmatched though. The M only makes you smile. I drive mine every day, I don't have a light foot but I keep in line most of the time and I get a 21 mpg average. This is all mostly city since I avoid the highway on weekdays but I did get a good 30 on highway once. With a lighter M Coupe, you should get even better mpg.
If you are concerned, get an S2000 but there is no guarantee that it will be a better car since those things are more likely to have been "abused", as a friend of mine found out with constant problems on his. That car is now fine but it took lots of repairs to get there.
The only negative with my M is that it makes me worry too much. It's a beautiful car and I worry about it all the time when I go to the mall, theater, dinners... oh well, when I get around to the NSX, this will be even worse I imagine.
