I've put over 120K on three different late model Caddys and had no W/P problems.
As an interesting note, when I first bought my Eldo back in April, I had the Caddy dealer take it into the shop before I took delivery, to (drum roll, please..) re-attach the door panels. While it was there, a technician called and said I needed a new water pump. Conversation went something like this:
CDT: Uhhh, we found a leak on your water pump - I think it's going to need to be replaced.
ME: Oh yeah? Well, that's cool - I just bought it last night and it has the 30 day/3K mile warranty, so go ahead and slap in a new one, it's ok with me.
CDT: You just bought it last night? OH..ok, hold on a bit, we'll call you back.
45 minutes later:
CDT : OK, the water pump looks alright. We put some dye in the fluid and let it run for a while, and no leak. I think it will be ok.
ME: Is the door panel fixed?
CDT: Not yet, we're still working on that.
Three days later, after shutting the engine off, I noticed a good spray from the hose connection at the W/P. I took off the factory clamp and put on a screw-clamp, and checked it a day or so later. No leaks. Six months and 4K miles later, the Eldo doesn't leave a drop of anything underneath it - no water, no oil, no gas, not even windshield washer fluid.
Moral of the story: Make them show you the bad water pump first. Even if it is under warranty, it's a pain for you, and $$Money$$ from Detroit for the dealer, and we all know that GM is a little low on cash these days.