Just bought a 4105 a month ago, 300 CX w/heavy duty bucket, Frontier Box Blade, and MX 6 mower. I have to say that the 4105 is perfect for my needs. It doesn't have the mid pto, but other than that, its been great. I am building a log home on acreage in eastern North Dakota, and needed something that could cut brush (CRP grass), work the driveway (1/3 mile), and lift extremely heavy red pine. I was comparing the 4105 to the 3520. While the 3520 has a lot more creature comforts and convenience items (cruise, etc.), the 4105 I must say has already proven to be an AWESOME tractor. I think the price for the tractor was only around $17.5 or so, a couple thousand at least less than the 3520.
So far, I have backfilled monster piles of solid and wet clay, moved over 60 yards of sand into our pad area, lifted and moved logs, and a lot of other things. The tractor has handled everything well without difficulty, and has actually exceeded my expectations so far.