It depends for me.  I used to have a bunch of pan 
cels, and I didnt like them _that_ much better 
than the normal cels.  They're also a pain in the 
rear to store if they wont fit in a cel book.  I 
like slightly oversized cels, but the really long 
ones tend to be trouble.  I think they look 
great, as long as most of the cel has something 
on it.  There's nothing like an oversized cel 
that's 50% or more blank, with the image just on 
one side or something.  My favorite cel is 
oversized, but it's not one of those really long 
ones.