Mini Coopers are cheap "premium" cars, in a sense that they are indirectly marketed as if they were mini BMWs (they are made by BMW), but they are just the equivalent of a volkswagen in terms of quality (which is pretty bad from professional experience). They are built using cheap parts, that are even too flimsy to even use (it is not an exageration, but actual experience).
Porsche is a brand that is driven by engineering, but engineering != reliability. Even though they have improved a lot in the last 5-6 years, they are not sold for their reliability, but for their performance. The Boxster is a specially good example of how not to build a cheap sports car when all you do is build premium sports cars. The best example of those shoddy quality of the Boxster (first generation) is the engine that self-destructed due to an improperly machined engine part (the case). Sadly, some 911 owners also got a bad engine with the 1999 model carrera equipped with the 3.4 engine (ddg it). The engine goes for about 12k when sourced from Porsche, not including installation.
Honda does not make cars that don't break. They have problems too. The Accord suffered from a defect in the engine block cylinders that cause it to warp the deck surface and thus make the car overheat (it required you to buy a new engine, because this was not serviceable).
The S2000 has a transmission made out of glass (not really, but you get my point(it is prone to failure on the first, second and third gear grear set)).
Mercedes does have the ussual electronic gremlic (just like most European cars), because they have extremely short development cycles, and you just can't test so much stuff at once (they ship a lot of buggy hardware, if you will). One of my favorites is the C240 Kompressor, which had a supercharged engine that blew up if you used a fuel that did not meet the octane requirements. Why didn't Mercedes just let the computer retard the ignition timing to compensate for the lack of octane? Wait, they did! They just didn't do enough of it (they did not test it throughly, and they also used parts that could not withstand a simple engine backfire ( a backfire is more lethal on cars that use supercharger or turbochargers, as it sends an explosion through the intake manifold (where the supercharger/turbocharger intake is)))(this comment looks like LISP code).
tl;dr: cheap parts, cheap engineering and cheap testing that derive from extreme cost-cutting measures make most brands out there a russian roullette. Good for mechanics, but bad for owners. Though with European cars, its as if you were playing Russian roullette with two bullets instead of one.
PS.If you do get the S2000, install a transmission oil cooler to extend the life of the tramsission components. The later years with the 2.4 engine had stronger transmissions, but a lower readline (and less peaky powerband (something people loved about the first generation (because it felt like a motorcycle/F1 engine))).
A lot of the stories I've heard about Mercedes Qc issues in the first part of the last decade is oil related. That in some case, they had issues when they first changed to an annual oil change maintenance spec using conventional oil. Then, perhaps on different engines, they had issues when advising a 12k or 15k interval (can't remember which) on synthetic.
Seems they learned from the mistakes around 2006-7 and from that point forward their maintenance spec is strictly syn (mobile 1) on a 10k, 1yr change interval.
I had oil analysis done on my last change, a 5.5l v8, which I ran for about 11k miles, and the results were very good. The oil probably had another few thousand miles life in it. Not that I'd push it, it was just good to know I didn't have sludge after 11k miles.
The engines had a coating applied to the cylinder walls that (theoretically) reduce frinction. Turns out the coating was a bad decision (it wasn't throughly tested (see a pattern?)), and they rolled back to their old way of building engines (which was pretty good).
I do think the 10k is not a problem with Mobil 1 synthetic. I've used that oil for about 15k on my own cars without complications.
If you want to learn more about the engine problems, you might want to ddg the words "mercedes benz nikasil".