I bought my 3320 hydro used, so took it as is. I wish it had a few more horsepower and a little more lift on the "X" FEL, but I think it's doing everything a 3320 is suppose to do. I'm pretty hard on in it and it has been great, one tail light bulb replaced in 350 hrs.
Other than oil changes etc. The big thing that helped it was reversing all 4 tires and liquid filling the rear tires, I can't believe how much widening the tires out and adding weight improved the stability. The extra weight slowed the top shuttle speed down just a little, it's now about 17 mph on flat surface and can go down to 11 mph on a steep hill, but I rarely use it on the open road so don't really care.
It's a great tractor and I would probably go with a 3720 if I had a choice, but the 3320 has done 98% of what I've wanted out of it. Also gets great fuel economy.