I've had reactions from both ends of the spectrum on the controls so it's hard to decide what's right with them. I think given time, they are fun to master and the smooth movement is very satisfying, but I also recognise that a 2 minute experience is not enough time for people to master the controls, so I totally get your point. I actually like the idea of constant movement, in fact when I play I rarely stand still (if you can call it standing :D)
The game getting harder just seemed like a given honestly, otherwise it would get boring if nothing changed for the whole session. But I guess that's also a matter of opinion.
I agree showing how long you have left to win probably would have been a good idea. I wanted to keep the UI minimal, but there could have been other ways to show this, maybe the balls flowing around the man could have started disappearing and when they all disappear you win or something like that.
Thanks a lot for your very detailed feedback, I really appreciate it :)