Thread bunching up underneath may mean that your top tension is too loose, or is incorrectly threaded. I had this same trouble with my 15" Bailey, and it was a top tension issue. I had changed thread, to a different weight, and neglected to adjust the tension accordingly.
As for Mid-Arms, I like my Bailey. I bought it used from a Quilt Board member and it has been quite reliable. There are other brands of mid-arms out there, and probably with more bells and whistles than the Bailey, with prices to match.