The benefit is of course that you've probably gone to your racial vendor to get your RIDING SKILL and the riding trainers are usually based near the mount vendor. While the basic flying mount is good, faster ones are available. Needless to say you need to further increase your riding skill. The ARTISAN rank of skill is required, costing you 5000 gold and requiring level 70. Again there is no discount. Each flying skill stacks with the others, so you will in total expend a maximum of 6435 gold. Getting your first mount: Most WoW players obtains mount from their own race's mount vendor.

You can obtain the mount item when ever you want, but you can't use it until you have the appropriate riding skill. You need to have RIDING at rank APPRENTICE to use it. Basic mounts allow you to move 60% faster than normal. So if you can move (for instance) 10 meters / second at a run, you can move 16 meters / second on a basic mount.

You can obtain a discount based on your reputation with the mount vendor's faction. When you obtain a mount, you get an item that can "summon" the mount, like a vanity pet. For instance you may get a Whistle or a set of reigns. You use the object to summon the mount, an you automatically mount it. The first mount you get is classed as a RARE (blue) Item, and will cost your 10 gold for the mount.