I have the 830 (previous model) and I love mine. One thing I never think to mention is that it NEVER "eats" my fabric, no matter where I start sewing! I don't need leaders/enders. I purchased the straight stitch needle plate to use when doing FMQ. I seem to have better results. I also got a spring FMQ foot (didn't like the "R" foot). It's a little different that I don't have to adjust anything...it's all automatic. I recently got the new walking foot with the snap in feet and a stitch in the ditch foot that snaps in. Love it! I've had it about 1-1/2 years and use it a few days per week usually. I can't think of any cons and would purchase it again. I am a Viking fan...had my last one for 16 years.
I think most issues are user error. Have them show you how to do the things you do most. It's got a cool buttonhole gadget, but I haven't made clothes in years! Love the decorative stitches.
Will they give you any classes with it?