Florida Mall is still my favourite, especially since it was refurbished a few years back, although I'm expecting it to be well and truly usurped by the Mall at Millenia! I think Belz has had its day - the Premium Outlets at Lake Buena Vista are much nicer.
We went to the mall at Altamonte Springs last summer which is owned by the same group as the Florida Mall. It made quite a nice change and there weren't many tourists, but it's not as good IMHO.
Celebration is lovely for a change of pace, although the shops are very boutiquey and the place definitely has a feel of the Truman Show about it!
We're planning on spending a day at Winter Park this trip.