I may be a freak, but I don't have FPS problems and I'm on an older laptop. Then again, I don't like playing past 40 FPS because I like to watch what is happening and before I found out Partial Print worked on my machine, I was playing in soup.
But the first and biggest obstacle I had was the default for tile size not being square. Aside from that, setting that could help plan out designations and buildings more easily (Outline, so instead of a full box you get just the outside lines) and being able to partially mark tiles (like putting a blue line over it in one direction or another without blocking site of what is on the tile) could really help keep starting players and make lifers much happier.
And just speaking from personal experience here, but I'd like a way to designate things on the fly, knowing that if something serious happens the game will either announce it or pause the game. And for many, many things that aren't serious. It is a drawback for me even now, spending so much time in pause doing grunt clicking or running scripts.
But as many people have said, a short introduction to the controls that give a set embark and has you learn some basic things would be a good option. I still don't have my mind all the way around ramps, as simple as they should be I have trouble getting them to face the way I want.