What the others said. Also, if you know a bit of the lore in TES, they have quite different cultural backgrounds. Since I roleplay my characters, this gives some nice input on what to do/what not. And beast races are just plain awesome

. Knowing that I am a lizard really changes my playstyle. Same for cats.
Edit: What would be nice though, is a bit more reaction from the NPCs. Sure, they tell my to keep my hands out of their pocket as a khajiit, but a bit of a wider array of commentary as well as maybe some reaction to the race would be nice. For example, as an Argonian I might get higher prices if I want to buy stuff from a Dunmer merchant (it does not has to be every Dunmer merchant, but some are definitely no fans of the people from Blackmarsh).