Since I picked my CVPI up 3 months ago (2000 model w/ 122K miles), I've replaced the brakes at all 4 corners, the heater core, and the front sway bar end links. It's come to a little under $400 in parts and I've done all the labor myself. As far as I'm concerned these are all wear items that just need replacing on a high-mileage car (except the heater core... I just lucked out on that one
I've also flushed the oil, coolant, and bled the brakes, but that's something I do first thing on every car I buy. All in all the car runs like a champ, rides really nice, and I like it. Considering the years and miles that have been put on it by the City of Tampa police force, I'd say it's held up pretty well.
I would say just drive one before you buy. Pay attention to noises, smells (something that would have warned me of my heater core leak), the way the steering wheel and pedals feel, the shift feel, etc. I got mine at a dealer that only sells CVPI's, and I crawled around and under probably a dozen cars looking for one with no signs of leaks too. Look under the front for signs of leaking oil, coolant, and power steering fluid, and check the bottom of the diff housing for signs of leaks there. I have to say most of the cars I looked at had some sign of leakage somewhere.