Honestly, no. I do not have any regrets about "going D.O." I think that the concerns about "being unequal" to M.D.'s is imagined. I have done an allopathic residency and fellowship and can honestly say that there is no difference. My advice is, whether you go to an M.D. or a D.O. school, do the best you can and be the best doctor that you can be. You will ultimately be judged on your abilities, not the initials on your coat.
This is the bottom line: There are many factors that go into what kind of doctor that you will become (personality, emapthy, brains, compassion, work ethic, etc.) I don't believe that where you go to school has alot to do with it.
You will find in the course of your career that those who bash others (for being D.O., IMG, whatever) are masking (poorly) some massive insecurities. I try to concentrate on being the best doc I can be. I really don't have time for other people's lame prejudices.
Good luck.