I think the importance of a regulator depends on how fussy a person is. I consider myself still in the learning phase, and I am not worrying about perfect stitches; I just want to finish some quilts for family. They look nice even though, if you examined them closely, you'd see uneven stitches. On the other hand, if I were quilting other people's tops, I'd be a lot more concerned about perfection.
I did buy the stitch regulator with my Sweet 16, but I decided to learn without it. I found that for some reason, I could do designs much better when my feet were involved in the process. So I am content to work slowly toward perfect stitches without the regulator. If you are a fussy type, I would suggest buying a different sit down than the Sweet 16, one that has a regulator that is built in. I think the Sweet 16 regulator is a bit of a pain to use. You have to move it around with the quilt.