I bought my 5525 several months ago, and like ddvinia, I have not had a single moment's problems. My only regrets are those that were caused by me, like not getting EPTO. /forums/images/graemlins/mad.gif
As far as how it would perform on the hills, I have no clue since the highest hill around here is a rice field levee. My final prices were about 22% off of list. I looked at the 6615 as well, but because it is a very popular tractor around here it was not discounted near as much. Also, because I already had a considerable investment in Category I and Category II implements, which I also use on my 4610, the 5525 allowed me get into more power and comfort and not have to buy all new tools to fit the Category II/III 6615. Overall, I'm very satisfied.