Topgun, it's really solid. I can hold the firearm by the forearm, and it feels just as solid to me as if I were holding it by the pistol grip. I used to have M33's on my M4gery, and the difference is literaly night and day. I'm waiting for my Knights rail covers, but after that, I think I'm done with this one (for now). I've already ordered more lowers and another M4 kit... this time, for my son. I'm going to get the .22LR conversion for it so that he can shoot to his hearts content when we go to the range. I somehow feel better with him shooting 550 rounds for $8.50 than 40 for $7.50.
Personally, I feel that I made the right decision with YHM. Price aside, it does everything I wanted it to do... getting it done at half the price of many of the competitors is bonus. With the money I saved getting the YHM, I bought another lower receiver.