Yeah I actually timed myself doing a slider puzzle to see if I could complete it before an average map loads, and I still haven't completed it. I think i'll do two types, a slider one for random play when you're bored, and a drag & drop one for loading. They're nice and easy, about 4x3 tiles.
Does anyone know if its a logical impossibility to complete a slider puzzle if they aren't square? I actually haven't seen one person complete this yet.