I did the same thing, only to realize that the regular flying mounts are the same speed as the free ones from K3 and the places where you can't use the free mounts, the epic ground mount is faster anyway. The only tangible benefit I can see in the short term is the fact that it opens up the shortcut flight to the flying base in icecrown.

If I had it to do over I would have spent the money on better gear at 80 to do heroics with and waited until I could do all epic flyers.