I have just begun machine quilting and have hand quilted things up to this point. I have a hand pieced queen sized quilt that I am definitely going to hand quilt because that's what I've planned for it from the beginning. At this point I would not attempt quilting anything larger than a twin size on my featherweight, but that has more to do with my confidence level than anything else.
My personal opinion on hand quilting vs machine quilting is that if it is hand pieced then it needs to be hand quilted. If it is machine pieced then it can be quilted either way, but I would be more likely to machine quilt it simply because that seems to be quicker. If finances were not an issue, then I would be prone to look for someone to do the machine quilting on a queen or king size.