I love my Bernina 930 that I bought in 1985. Every stitch is perfect. Two features that I especially enjoy are needle down and ability to drop the feed dogs. Having a walking foot is great. I also have a newer Bernina 440 and the only better feature on it is the stitch regulator for doing fmq. So far I'm still having to practice a lot with that.
I do agree that basically you will use a straight stitch 99% of the time so there is no need to spend a lot extra for fancy stuff you won't use.
I do wish my machines were lighter in weight to make them easier to take to classes. I'm afraid you may give up longevity with the cheaper plastic machines.