I have the Bernina 440 QE with the stitch regulator and I love it. Friends have Viking and Pfaff and love them too. I made the decision mostly based on having a really good service center for the Bernina nearby, and I bought an extended warranty because I can take the machine in as often as I want for adjustment, cleaning, whatever. I am very happy that I purchased the stitch regulator, but not so happy that I got the embroidery module. It turns out I'm not so interested in doing embroidery.
It's really important, if you buy a higher end machine, that you purchase from a shop with a good reputation for service. In my case I got quotes for price at the Puyallup Expo, then took the Bernina quote in to the local dealer and he matched it.