First, I really like my 3320 with 120 hours, very strong, overall excellent, reliable machine, that looks like it will stay that way for many years.
That said I did have some problems with mine, in fairness it was one of the very first ones available in our area. very early production, broke one of my normal rules "never buy first year production"...
The first problem was the PTO not disengaging (5 hours), took three trips to the dealer to finally resolve (they picked up and returned each time). Turns out the early units weren't getting all the machining residue out of the cases, which plugged some small orifice. The first fix was drilling out the orifice, second time cleaned it, third time, 60 hours they replaced all hydraulic fluid, and filters (for free), excellent dealer! Seems ok now.
Second problem was leaking front axle seals, I don't run in water or mud, although I don't see mud as a major obstacle. Seals replaced under warranty at 25 hours, no problems since. (and I definitley use the machine harder now)
Third problem was the early casting issue on the quick attach bucket brackets for the 300CX loader, replaced under warranty with the new version. (btw - the 300CX is an incredbly strong loader, very conservatively rated in my opinion) Highly reccomend filling the rear tires, and using ballast as outlined in the manual!
Finally, not a problem according to Deere, but I am still dissapointed the loader valve doesn't allow smooth blending of functions. Mine, and the few others I have seen do not allow two functions at once with any repeatability. It can be done if the stars in heaven all align properly... The commercial equipment, and Kubota CUTs I have used all do this effortlessly. I don't know if the later models have different valves. I will say, if you are not using it to make a living, you probably won't care. Everything else about the loader is excellent.
I know that's more than you wanted, you asked though! Honestly it's an exellent machine, I'd buy another tommorow if I needed one (might opt for for the turbo, deep tilling can drag it down some) I can also second the good dealer issue, without good support I would have sold it and bought Orange. As it is I'm glad I stuck it out.
Hope that helps you!