I have a 900 Nova. The stitch selection is not the largest, but the utility stitches are there. It runs fine, a few more plastic gears than the 700 series and earlier. That said, this machine is the same standard as the 800 series, and the 900 is made to be extra portable with a handle on top of the machine, not just in the case. If something is wrong, a repair is well worth it. It weighs a bit less than the Records, but I think it's just as capable. I dare say it should zigzag perfectly, it has the tension mechanism and CB hook / race Bernina is known for. It's rahter forgiving when it comes to upper tension, but if you sew a lot with top stitch thread you might need to get the special bobbin case for thicker thread. The only reason I haven't is the price.
Before anything, I would clean and oil; the top of the machine (two screws) and top of the freearm comes off (spring release, upper left side behind the bobbin cover). Take out the needle and presser foot before the top of the freearm, it prevents scratching the finish. There are oil points behind the face plate. The bobbin case and hook comes out easily. There are
a few tutorials on the web for light DIY service and repair if needed.
From my experience, it has the same stitch quality as the Records (which where the top models. I have compared to the 730 and 830, and didn't notice much difference. Bernina has neater zigzag than many other machines, new and old.