My wife purchased an 06 DTS with 34k kms on it last September. Our first Cadillac it replaced an absolutely trouble free 04 Buick LeSabre with over 100k kms on it. Main reason for buying it was as a good and roomy highway cruiser for our annual trip from Nova Scotia to Florida.
Positives: Beautiful looking car, it was in mint condition, comfortable multi adjustible seats, very quiet and smooth on the highway, all kinds of gadgets, one I like is the warning system for parking. The engine is smooth, powerful and relatively fuel efficient (not as good as the Buick V6). Trunk is huge, and we need this for the trip.
Negatives: Unfortunately we have been in the service department more often than ever with the Buicks. First we noticed the heated/cooled seats did not work. Then we got a recall for the windshield wash heater. On the trip to Florida almost all the anti freeze came out (probably due to the service dept leaving the top off the reservoir); in Florida we got the seat heaters fixed, and the recall looked after. It was also in for a knocking noise in the back which turned out to be a release valve in the gas tank. After a tire rotation we needed a new tire pressure monitor sensor. A new cabin air filter cost $90! Trip home was uneventful, but after we got here the driver's door stopper had to be replaced, we needed a new tie rod end, and after it had been in for those repairs the battery was dead three days later.
We still love the car in spite of these issues, but they are annoying, and although a couple of them could be blamed on service, they are just too numerous to make me feel we have a reliable car. We will probably keep it though as you cant get much for it. I think we'll definitely be getting the extended warranty though.
We had five Buicks and never had this many problems. The last one hadn't even had a brake job at over 100,000 kms and all it ever needed was regular oil changes.