I've got an old JD 440b, it's a good little skidder for what it is. It's small enough that I can jump it on a gooseneck trailer and move it with my pickup. It only weighs about 12,000 lbs. but that can be a detriment when on steep ground. If you're skidding on anything other than flat ground, you'll want to load the tires (your seat cover will thank you). A little more width, and a little more weight and you could get some real work done, but then you'd have a 540.
What else can I say? They're good little skidders, as far as little skidders are concerned.
Andy