here is a quick list of things i have experienced with my 2006 V (79K miles), and what remains. just a datadump, and perhaps this will help others:
36K miles: replaced diff bushing with CS unit. did not see any issues with stock unit. also replaced diff fluid with royal purple. hoped it would fix the whine. to this day, it has not.
75K miles: sticking/lack of a rebound in clutch during cold weather. shop found a leaking master cylinder and replaced. At same time, I had the tranny flushed and a serpentine belt/idler replaced. idler was starting to squeal. I also had some problems getting it into reverse. thought this was due to clutch or the transmission. the problem remained.
79K miles: with all the clunks and the remaining reverse issue, I decided to buy a trans mount and level 2 motor mounts from Creative Steel. these were replaced by a service shop. both motor mounts were busted, but the tranny mount was intact. soft, but intact. the motor mounts are busted at the top end, so the vertical travel is about 1/2 inch. the differences I have noticed: no more bumps/clunks in driveline. the engine is far quieter (used to have a lot of rumble). I was worried about vibe from level 2 CS mounts, but it is practically zero. this service also eliminated the 2200rpm harmonic vibe I had in the car, and the overall driveline vibration is nearly gone. less diff whine. when they did the service, they also replaced the starter. there was a cracked/bad connector into the starter. they said changing the starter would have required dropping the subframe, so it was partially done as insurance. I really recommend the CS mounts. I don't hodrod this thing, so I figured the engine mounts were still intact. everyone should replace stock mounts by this time. I waited too long, by a couple years, to do this.
79K #2: I still have something loose in the front end. I can hear something loose when going over a bump. I expect it to be the sway bushings, since all the usual stuff that goes wrong in these cars has happened to me. I have bought sway bushings from CS, and also bought a complete set of upper and lower control arm bushings from them. I'll be buying upper and lower ball joints (moog) and wheel bearings for the control arm service. I'll likely do this over a weekend (neighbor, actually). After this, ill have the car into the alignment shop (and also have the tie ends replaced).
Every winter (I drive this thing in michigan), I have all stability/abs stuff go out on it. the common denominator seems to be super cold weather. I thought it was the steering position sensor, but found (with digging on a Tech II), there is a solenoid sticking in the EBCM. I have not addressed this yet. the fix is another $800-1000. I am considering a complete flush of the brake fluid, as I have never done it. hoping this will help the solenoid.
I can tell the dual mass flywheel will need to go at some point. ill do this when I do the clutch upgrade.
Besides the above, the POS infotainment button chips (shame on you, GM interior engineers), the electrical gremlins in my sunroof, all the crap-plastic A and C pillar cover screw bosses dissolving (another engineering shame moment), the poor anti-reflective coating on the Nav screen, the pig-rich engine mapping, this has been a good car.