From my own experience I'd say that if you are below 1500 you are going to have a hard time even with the easiest level. Actually people complaun that the simple level should be easier.

But I you are above 2000 and you are used to computer chess then maybe the game is not so tricky for you once you find the way to break its "strategy". I don't, never found myself in that fortunate situation.

I wish someone would work on a freechess client and a port of scid using the databases publicly available. I even had some mockups drawn so time ago...