After 2.5 years of ownership and 35,000 miles behind the wheel, I had to let the 2005 XLR go. I bought the car from a private party w/ 53k miles and got to 88k before having to call it quits.
I know many of you do not use this car for a daily driver (good idea), but I've put it to the test over the last 30 months. The following are the issues that I experienced and fixed (mostly in the first year):
1. Leaking radiator
2. Water Pump Failure
3. Shifter Cable Failure (Left me high & dry, had to be towed)
4. Glove box lock/handle assembly replacement
5. Aftermarket gas cap replacement (original is duly noted as not fit for service)
3. All new belts
The following items were recently found during an oil change and recommended:
1. Rack & Pinon PS Fluid Leak (Complete replacement recommended)
2. Front Cam Seal Replacement (They have "weeped" since I bought the car and have only gotten worse)
Lastly, these are the other issues that just generally prompt me to step away and run from this cash pit...
1. Roof seals leak through the door a/c vents after a hard rain.
2. Leaking roof seals caused the power lock on the driver side to fail (a/c vent is located right above this switch)
3. In the last year the roof would not cycle down. Randomly it would work, but generally always sticks when the top is supposed to roll back. Did not work at trade time

4. Solenoid valve that releases gas cap cover would stick OFTEN. I mastered picking the lock with a credit card.
5. FOBs randomly "reprogrammed" and would not allow all user options to be accessed.
6. 6 disc changer would not eject properly (sometimes)
7. Very noticeable transmission "shutter" in 2nd gear at certain RPMs
8. Over the last 3 months the "service fuel system" message has been appearing the DIC. Prohibited the computer from giving a gauge reading. Generally fixed itself after "sloshing" the fuel around in the tank. I pinpoint that this failure often occurred after going up an incline (i.e. highway on ramp)
9. Way too much heat dissipated into the cabin from the drive train. Very uncomfortable on 5+ hr drives.
10. The melted DRL lenses just absolutely made me furious every time I looked at the car. GM made an obvious engineering error and would not own up to it.
I'll stop here but just wanted to share my experience. I gained much valuable knowledge from this site and truly thank all of the members. The amount of time I spent here, actually speaks to my experience with this car. You would think for this kind of money a guy could spend more time driving and less time trying to fix one of the cheap components. I took a big hit on the trade but couldn't be happier in my new 'burb'... GM Warranty Purchased!!!
GOOD LUCK ALL!!!