Justin, I see what you're saying about {{#if}} not working with transitions. My solution only works with removing from extended can.Lists and adding in general. I'll have to really think about this, because the solution needs to be simple and seamless. I think that my solution still applies to Lists in order to maintain default CanJS behaviour, however. If an index has been removed with splice/pop/shift, it should logically be gone even if it's in a transition state. This is the only real performance hinderment.
Alex, I think he's referring to my "transitionsend" event, which is part of my jquery.transitionsend plugin.