The master riding skill will increase the speed of all of your 280% flying mounts to 310%. Nethaera posted (http://forums.worldofwarcraft.com/thread.html?topicId=27026400553&pageNo=3&sid=1#53) that you'll automatically get this skill if you've already got a 310% mount, but I'm afraid that I'm not able to confirm that myself.
If you don't already have a 310% mount and want to buy the skill, it'll cost you 5k gold. The good news is that you can get faction discounts, so Wind Rider Sabamba will sell it to you for "only" 4k gold if you're exalted with the Warsong Offensive, and this I HAVE been able to confirm. She's on the southeast landing pad on top of Warsong Hold in Borean Tundra.
I've also seen posts that people haven't been able to ride their carpets or flying machines after upgrading, because those "require artisan riding skill." I have no idea if this has been fixed in 4.0.1 on live.
There's a known bug (http://forums.worldofwarcraft.com/thread.html?topicId=27292691674&sid=1) that the Violet Proto-Drake that you get from the achievement What a Long, Strange Trip It's Been is NOT currently awarding master riding when you mount it. They'll be hotfixing in a patch (sometime) so that you get the skill automatically the first time you mount the drake after the patch.