Currently I follow Theravada tradition, however I have been many times to NKT temples/meditation sessions and I also did a retreat with FPMT in Nepal (traditional Tibetan Buddhism that follows HH Dalai Lama), so I have been there...
Yes, there are some disagreements and controversy, but I will not write my opinion on the controversy as I want to respect all followers of Buddhism. If you search on google or youtube you will find many pages and video documentaries (even a BBC documentary & Swiss documentary about it). Most of the controversy is about the worship of a "Dharma protector spirit", the Vinaya in NKT and about their leader that claims to be a Geshe and FPMT doesnt seem to agree with it.
In NKT temples I only found nice people and a very kind monk, but I left because of the library: 100% of the books there were written by their leader Geshe Kelsang Gyatso, that bothered me, I was looking for the suttas and the words of the Buddha, but could only find Geshe K. Gyatso, sometimes it made me feel like being part of a cult, so I left, but I repeat: I only found nice people there, no regrets.
My experience with FPMT was very good, the library was vast with many different authors, but again I left because I felt like Tibetan Buddhism was mixed too much with local culture and other religions (astrology, shamanism, tibetan book of the dead etc...). But once again: Only found nice people and great monks.
In Theravada I found what I was looking for, but do not take my opinion as something right, I do believe every path to Buddhism can be holy, it is more about what feels right for you.