The Bernina Sport is a wonderful vintage machine and a real workhorse. Whether or not it is worth $300 depends somewhat on its condition, the accessories that come with it, and the area in which you live. Here is a link to "completed listings" to see what they have sold for on eBay:
http://www.ebay.com/csc/i.html?_saca...mplete=1&rt=nc
You could certainly quilt on a Bernina Sport -- powerful motor and superb stitch quality; however, the harp space is limited.
In my opinion, vintage Bernina's are worth the cost. I have a Bernina 1230 that I would never give up, and a smaller older vintage Bernina that I keep for sentimental value. But keep in mind a vintage machine will not have the needle-down feature that many of us have become addicted to in the computerized machines!