It's not perfect, but it works. It has the standard buttons overlayed on the image for "Use", the "A" button and item menu. The movement joystick only pops up where you put your finger down, so that kind of helps avoid blocking any crucial part of the screen with your thumb, but it still happens from time to time.
As for timing, the controls are relatively responsive once you get a feel for it so it's not as much trouble as it might sound. Of course, the tacked on save/load feature helps immensely. I've had my share of fuck ups because it's just not the same as using a controller, but it hasn't really hindered me in any way. I've made it to level 4, past the game show playing on Normal.
TL;DR Controls are okay, not terrible. Hasn't impeded my game progress.
