I'm actually guilty of not riding my faction mount, the closest I ever got being the Swift Warstrider. I currently use the very awesome but all-too-common Black War Bear (every day, it's like 40 more people pop up with the mount), and for flying I use the not-so-common but also not-very-awesome Albino Drake. On my engineer I'm enjoying the Turbo-Charged Flying Machine and I plan to get a motorcycle when he dings 80. If I could afford Salvaged Iron Golem Parts and everything else, that is. There are really quite a lot of mounts to choose from, which is probably why the easily acquired, 'vanilla' mounts aren't as popular.
Later in the thread, Eyonix mentions the distant possibility of bat mounts being added to the game (this is Blizzard, though, so don't hold your breath) in response to one player asking that the Undead get their own racial mount just as how Night Elves get to enjoy their Hippogryphs. Well, Night Elves and rich friends of those Cenarion guys. Blizzard mentioned somewhere that they would be adding more mounts to the game to make the 100 mounts Achievement more... achievable.
Bat mounts are certainly a nice possibility. The WoW TCG has some great mounts, like the Spectral Tiger and Nether-Rocket X-TREME. There's the unique Reins of the Raven Lord. There are just a lot of mounts now that I've never really stopped to think about what mounts I'd actually like to see in the game. Mulling it over, though, I wish there were actually a nicely colored Wind Rider. I mean, the Armored one in Dalaran is sickly pale blue. Why isn't there a Black War Windrider? I mean, that'd be a great Honor sink. What other mounts do you think should be in the game? Should there be cooler versions of the racial mounts? Maybe a bonus if you ride your own race's mount (Eyonix was quick to shoot down that idea)? The possibilities are endless.