I love how much detail this program has, it is very easy to use with all of my experience in other programs such as Maya or Cinema 4D! It's not really anything that i dislike about frag motion so far but there isn't any features yet which are missing from what you can do right now either unless they have been added since we last used them -.- So everything seems great for me atm :) The fact its free would be nice too though :).
That being said nothing specific comes up when using this product just make sure your familiar enough before purchasing because if u dont know ur going into trouble haha.