We've had a 6220 for a little over a year. Overall, I think it is well built. I've heard the Powerquad transmission is preferable to the IVT. I can't speak to reliability as ours is fairly low-houred, but the components seem to be well built. My main gripe is the amount of sensors and plastic on it, mostly because I grew up with Farmall Hs, Ms, and 20 through 40 series John Deeres (3020s, 4020, 4240, 4640 etc). The 6000 series are a handy size for loader tractors, and still have adequate power for PTO work. MFWD makes them pretty gutsy too.
I wouldn't be afraid of another one.