I just bought an Arctic Cat 400 last year. 4x4, auto tranny, more ground clearance and suspension travel than any other 'wheeler. For a little over 4 grand, I don't think you can go wrong with a Cat. I have absolutely no complaints about mine. They all have their pros and cons, so it basically comes down to personal preference. I just use mine to scoot around my 40, a little bit of work and a little bit of muddin'. I checked out all the others, and figured the Cat was the one that best fit what I was looking for.
I know fourother guys that bought Cat's the same time I did. They are all pleased with what they got as well. One guy got the 500 2-seat model, another got a 500 and a 400 for his wife, and the other 2 guys got 400's.
We all got them within a few months of eachother, and none of us have had any problems.