Lots of discussion on that for any car/truck purchase, and lets face it "Discussion Groups" do attract many that are un-happy. But here I believe you will find mainly those happy with the design and love their Nitro.
Sure there are issues that need to be addressed and many have found answers here. You have a very good lifetime warranty on the power-train with a new purchase and I myself fortified that adding extended warranty coverage (see post on that subject). Early on it was apparent that the R/T series seemed to have far less issues since it has a different engine, transmission and suspension. That is what I chose and couldn't be happier and plan to keep it a very long time.
However any 08 Nitro now should be very dependable and enjoyable to drive. Look over all that posts here and on other Sites. Most past issues have been corrected in production, or by Dealerships in-the-know, it was just a rough start that all Nitro owners see in reviews by trade magazines. Too bad they don't do a follow-up with a year newer model, but they just don't.
Being close to the February New Chrysler kick off, I would wait to see what is going to be added to the Nitro (if anything) and if any Nitro models will be discontinued. All of this has been posted here and we should shortly know what the future hold.
Again I wanted what I bought and could not be happier. Good Luck with whatever you decide. This is your best source as to what owners feel about their purchase, forget about Car Magazine articles or reviews, or salesman. They are all trying to sell you something! You learn the truth from Owners.