Have you ever noticed that the bottom of the MBP gets hot if it is sitting on a flat surface?
Therefore, cooling can occur on the bottom of the MBP.
So in actual fact, notebook stands, and those with built-in fans do aid in keeping the MBP cooler.
A decent stand that suits the aesthetics of the Mac is the
mStand by Rain Design.
I can't comment on the 'gel' mats as I've never come across them.