I looked around a bit on this forum and am getting a bit nervous. Looks like lots of possible problems to arise. What the typical problems that the '05's have? What should I be checking prior to purchasing? Is an extended warranty a must? Thanks!

Keep researching. This topic has been addressed here ad nauseum. Every question you've asked is here.

There are many more owners without issues. Spend a couple of nights (or weeks) reading and make up your own mind.

--As a general rule, owners without questions/problems don't post. This isn't a car for people who think they're getting a good deal based on the original sticker price. Parts avilability isn't assured. Cars break. Wallets empty. Warranties expire. Do your homework and you'll have a wonderful car. Cut corners and Murphy will find you.

I looked around a bit on this forum and am getting a bit nervous. Looks like lots of possible problems to arise. What the typical problems that the '05's have? What should I be checking prior to purchasing? Is an extended warranty a must? Thanks!
A basic starting point is to be sure the car you purchase either IS up to date service-bulletin wise or WILL be brought up to date at no (or known) cost. That done, you have eliminated nearly all of the "typical" problems. That's not to say there will be no problems, but it's a good start. A warranty is good, unless it's one of those 3rd party ones, which are generally crapshoots. But, if the car checks out ok with a Cadillac dealer, a non-warranty vehicle may not be a huge gamble. You want to be within a reasonable distance of a Cadillac dealer with an XLR-qualified technician.

I bought my 04 as a cpo, had an assortment of problems fixed under warranty, and have now been out of warranty for 6 months without any new issues. Yeah, I'd like to have some coverage, but then each month that goes by brings me closer to any needed repairs costing less than the warranty.