For one, Jeep is discontinuing the diesel in the Liberty because it is an outsourced engine, made my VM Motori of Italy. Daimler-Chrysler will be introducing the Grand Cherokee Diesel at about the same time as the Liberty Diesel is going out. The Grand Cherokee Diesel will be running on a Mercedes Benz Bluetec V6 common rail deisel that is reported to have cleaner emissions than 99% of cars on the road. The Jeep Commander Diesel is soon to follow.
Mercedes Benz knows diesel and makes some of the best diesel engines in the world - not to mention it is easier and cheaper to keep these things "in house."
Expect to see lots more Jeeps, Dodges, and Chrysler diesels in the future. Even Honda is looking at importing their diesel Accord soon.
As far as buying a diesel Liberty now, I have heard excellent things about its reliability and performance. You'll just have to test drive a V6 and imagine it with more power, better mileage, and a bit more noise at Idle. A lot of the TDIClub members are buying them and loving them.