What bugs me the most would have to be the legends. The letters feel like bumps on the keys, which after the Model M, I could do without. At the same time, the keys feel slippery when compared to the Model M.
I cannot describe it well, but the Model M keys have this roughness to them that speaks of quality, as backwards as that sounds. They feel... sturdy, like they aren't going anywhere and will be around with the roaches after the fallout. The QFR board itself? It also feels weighty, but the keycaps make me think of your average rubber dome. They look neat, but do not feel that great on the fingertip. At least to me.
Beyond the keycaps, I only have (so far?) two complaints. Firstly, my backspace is squeaky, but if I understand things right I just need a bit of grease for the stabilizer(s?) Second, the key cap puller doesn't feel that great when I use it. I get nervous about yanking out the switch. Not sure if that is the puller, or that I have only had the board for a few hours so I am nervous about damaging it!