I have the HQ Sweet Sixteen and love it (Babylock Tiara is the same machine, and I suspect the Viking sit down that you looked at is also made by Handiquilter. I haven't confirmed it, but I've seen it at a couple shows now and it looks identical to the HQSS). I did by my HQSS without the stitch regulator and have not regretted that decision.
I prefer moving the quilt under the needle to driving the machine over the quilt. (Though I would love to be able to skip the basting).
Cheers, K