The minuses:
(1) The groups founded on him are cults. ( Versions of the Rimbardo prison experiment.)
(2) Groups founded on him are innocent when it comes to science. But his paradigm of believing in all saints (tzadikim) can solve this problem in potential, since believing in all saints (tzadikm) includes Maimonides who made it his major project to marry Aristotle and Torah together.
The innocence in regard to science is also a problem in the Litvak world (see Genesis and the Big Bang) but at least there is acknowledgment of the validity of science in the realms where it applies.
Pluses are he was a true tzadik filled with great advice. If people would not have turned his "thing" into a cult, he would be a great role model.
The major issue with Reb Nachman is the movement he was involved with was put into excommunication by the Gra for good reasons. Reb Nachman by himself is obviously amazing and fantastic. But combined with that movement, that ruins the whole thing.
Appendix:
1) The Rambam (Maimonides) had a system. The idea of his system was that in the Torah there are no contradictions. and he expanded that to include the Talmud. So in his system there is no contradiction between Torah and Talmud. Furthermore he also had a modified Neo-Platonic and Aristotelian system {that he does not define exactly} and this system he assumes is the underlying world view of Torah.
The idea that there is no contradiction in Torah was common in the Middle Ages. It led Aquinas to create his system based on his idea that there is no contradiction between the Old Testament and the NT and later people called the church fathers and Boethius. This is very different from today when people feel they individually interpret the Torah to mean what they feel it means to them. Or when groups interpret the Torah to mean what it means to their particular charismatic leader.
There is no idea that the Torah is a self constant whole that means something very specific and and nothing else. and that meaning can be discovered by human reason. For if it could not be discovered then why was the Torah given at all in the first place? So in terms of understanding the Torah we have to call the Middle Ages the "Age of Reason." the period stated after the middle ages we should call the age of darkness.
Even in Musar you can see this. Musar had three distinct periods: (1) The Middle Ages, (2) then all Musar became Kabalistic, and then (3) the post Israel Salanter Musar which was getting back to \the Talmud kind of Musar
