I see definite problems with Messianic Judaism.
The biggest problem I've seen is the slippery slope to self-righteousness. I have been told by them that I would be least in the kingdom of heaven for not believing as they believe.
What horrible thing am I doing that will make me be least in the kingdom of heaven you might ask...teaching that we are not under the law.
So, while keeping the old testament holidays seems like a great idea I believe it is a slippery slope into legalism and self-righteousness. But, then I don't think that the Messianic Jews have cornered the market on legalism and self-righteousness. That is something that we all must fight against. I do believe however any time you try to put yourself back under that law you are making a horrible mistake.
They will say that they are not under the law, but in the next breath tell me that I will be least in the kingdom of heaven if I don't join them under it.
I use to watch Jewish Voice years ago. I remember one of the hosts, I think her name was Chira--not sure. She had commented on how she thought it was fine to keep the old holidays, but she couldn't understand how some of the Messianic Jews became obsessed with keeping them. I understand it--they have a hook--the yeast of the pharisees.
RO 10:5 Moses describes in this way the righteousness that is by the law: "The man who does these things will live by them."
I've actually seen them quote RO 10:5 above as a good thing. To me it is a warning. We don't want to live by anything other than the gospel as the continuation of the above bible verses makes clear:
RO 10:6 But the righteousness that is by faith says: "Do not say in your heart, `Who will ascend into heaven?' " (that is, to bring Christ down) 7 "or `Who will descend into the deep?' " (that is, to bring Christ up from the dead). 8 But what does it say? "The word is near you; it is in your mouth and in your heart," that is, the word of faith we are proclaiming: 9 That if you confess with your mouth, "Jesus is Lord," and believe in your heart that God raised him from the dead, you will be saved. 10 For it is with your heart that you believe and are justified, and it is with your mouth that you confess and are saved. 11 As the Scripture says, "Anyone who trusts in him will never be put to shame."