I have thought hard on the basic aspects  Nachman from Uman and my basic feeling is that his advice and ideas are very valuable. It is not that all the groups founded that go by his name are very good but that he himself had very important ideas concerning Torah.
The main problem is that people generally associate his name with the groups that the Gra put into excommunication.
 It is a problem that his good ideas get used to seduce and influence others to do bad stuff.