So I have a 2.2 manual and a 3.2 auto, so having biggest gap in terms of performance and DIY work ect.
Headgaskets, yes they fail, but this for me is down to coolant service. My 2.2 is on 179.2k and it's on it's original head gasket. FatherT's 2.2's HG failed at 99k, but that was dealer serviced in it's first 100k (was a fleet car)
I'm on my 3rd exhaust flexi, original GM one failing not long after 100k, new one lasted 60k (from Camskill) - It's also had one cam sensor change, again at around 100k and it's cam cover has been done once, again funnily enough at 100k miles. It's had a new stat too, but can't remember when. Well over 100k though. Usual suspension stuff, wishbones, shocks ect.
The 2.2 is a pleasure to work on in the engine bay, soooo much room. Cam cover is a really nice easy job, as is stat and cambelt.
It's never let me down and even after abused in London for a couple of years and services slightly neglected, I took it to Austria and back and never missed a beat.
The 3.2 so far, has yet to put a foot wrong either. It's had new exhaust, wishbones ect. But it's going fine, it's a different beast to the 2.2 though, much more effortless on the commute. Though not on the wallet!
My 2.2 has a far smoother idle though and less engine noise, you are not going to win any races in the 2.2, but it's actually more relaxing to drive. Because I know I won't win, I don't bother. In the 3.2, because I could challenge most things, I don't relax as much

Also because the 2.2 lacks power, it saves the rear tyres. 30k is easily achievable. I got 48k out of my first set, which came with the car! The 3.2, going to be lucky to get 12k....