For me, ease of use considers both execution and practical extent of character depth. I'll be the first to admit that I'm put off by a certain level if execution in order to play a character to a standard effectiveness: if I -must- learn a number of very tight links, complex inputs unsuited for a pad or combo lengths that even I can't wrap my head around in order to play a character well, I will find them intimidating to learn and pick up rather than rewarding, leaving me most likely avoiding them. Having played MvC3 for a long time now, however, combo length is far less of an issue than it used to be. Developing intuition with a character's tools is something for me to consider as well, and that is more to do with how comfortable I am with a character as opposed to the extent of their strategies and tactics. If effective use of their tools eventually comes naturally to me, however vast or limited their depth is, then I will be highly likely to stick with them.