no, there shouldn't be. converting BACK to fat32... thats a different story... and I think according to MS is not possilbe, although I've heard of ways to do it.
Converting from FAT32 to NTFS will give you huge cluster sizes... i mean big... like a gazillion KB... oops.. maybe not that big. J/K str8lazy. I read the cluster size and i was like whoa dude...
How big is your hdd BTW? Can you afford the slack space that this going to create?