Best: Any WM kit. I've built 4 of them, CAP232, Ramber 30, ZEN50 and they have all been a breeze and as long as you follow the recommended engine size, is a sweet flying machine. Even the engine mounts go on without ado... blind nuts installed for it and all. Only one that was a little more challenging was the WM Cub .26 because you have to drill your own engine mount mounting holes (oooo.. hard work), windows weren't a perfect fit and it was just so small that I had a hard time working on the insides... but once again.. as sweet plane once its together

Worst?: CMP (Chief) Cessna Skylane - the fiberglass fuse was so imprecise that there was at least 2mm gap between the stab and the fuse.