I have has my C36 AMG for over two years with none of the above issue (well no issues of any sort)
To put it into context I ran the first one for 3 years and the second for 4 - so a total of 7 years. I took the first one from the 50k mark to the mid-70's and I took the second one from the 70s to low 90's.
Consumables/Items that tend to fail
Both had failures of predictable and relatively cheap wear and tear items - crank sensor, brake light sensor, steering damper, lower front ball joints. The ball joints wear badly in London due to the proliferation of speed bumps. out of town that wouldn't be such an issue. Front discs are expensive so make sure they've been replaced or budget for them.
Bumper Covers
Due to parking errors (reversing into a hidden bollared and a hard-to-spot post) I cracked both rear bumper covers. Had the first one plastic welded, left the second one as it was as I traded it in for my current 211. Worse damage could have meant a new AMG bumper cover which is not cheap.
Ignition
On the first one I had an error code suggesting that there was a fault with the lambda sensor but it turned out I had two faulty HT leads and a dodgy coil pack. I use a good indy (BSG) and they diagnosed this. Just beware as there are 16 plugs, 16 leads and 8 coil packs. Advice; make sure the previous owner has changed the plugs or budget for it. (I never had to do the plugs on either 43 and fon't expect to have to do so on my current E500 as the've been done).
Gearbox
I didn't have any problems but some people have had. If the box has been replaced (by someone who knows what they are doing) this is a good thing. In any case check to see if the g'box fluid has been changed and if not budget it in.
Exhaust
I never had a problem and haven't heard of someone having one but if you do they are eye wateringly expensive). Like the bumper covers probably more of an accident damage issue that anything else but, like disks, AMG $$$ items
Rust
The fist one had great paint. The second one was pretty shocking. The arches went at 8/9 years and were going again when I flogged it. Has to get the sills patched (!!) at 10 years. The bodyshop said they had rarely seen such a poor finish. The base coat didn't seem to be properly bonded to the shell so stone chips lead to water getting under the paint and then rust. This was a 99. There are lots of rusty Mercs of that era out there.
Dampers
The first one was fine, the second one was needed new ones in the low 90's
So, in summary, I never had a massive failure. I did spend a fair amount in some years on maintenance (£1500+) but on others far less.
The rust was the biggest issue - the car would have needed a full bare metal respray and even then I think it would have come back. It didn'y really matter to me as I was going to trade it anyway but would have been a massive b*ll ache if I had not had that option.
Did I like running C43's? Yes, very much so. Would I recommend a good one? yes very much so. I'd suggest buying the very best you can, with stacks of history.