There's plenty of info regarding common issues with the early 04-05 XLR documented on this forum. If you take the time to read through the posts, you can deal with them if your vehicle starts to exhibit any of the symptoms described.
My biggest complaint/problem is the unbelievable amount of squeaking, thumping, etc. I hear in the passenger compartment (especially when moving).
It's sad a car sold at 75k originally is in this condition at only 12,000 miles.
The minor changes for the '06 XLR included the addition of Adaptive Forward Lighting, some different exterior colors, a hidden XM antenna, and the replacement of the unsightly "wart" on the rear decklid. The big change was the introduction of the V model with a supercharged engine, larger wheels, (19") raised hood to accomodate the supercharger, thicker front and rear sway bars and $25k increase to the sticker price.