Worst experience was a Guillow's Piper Cherokee. I admit, part of the problems where the fat fingers, but it was really hard to get things into place.
After glueing several parts to my fingers, I gave up on that one.
I just finished one of the best kits I have seen so far - BTE Vortex. Very detailed instructions and high quality materials. This is so much fun to build, I wish all kits would be like this.