The best thing about the 15-20 level bracket is that you get travel form at level 16 and you are within grasp of cat form. Things get progressively more difficult to kill through auto-attacking with the mace, however if you have the money to upgrade armor you can do a fair amount of AOE killing in bear form as you now have Swipe. I ended up doing that myself because it was just too painful to endure auto attacking any more.
I did end up going to the Blood Elf zones to level as I understand the leveling experience there is generally easier, like I know it is with the Draeni start zones. It probably won't be the case much longer as all the zones in old Azeroth will be redone come Cataclysm, but for now I really do recommend saving yourself some time and making your first act as a new character to get to the Draeni or Blood Elf starter zones. In any event I burned through this level bracket not only because of the zone but because you can use the Looking For Group function as well. Two dungeons, despite them both taking a fair amount of time to clear, netted me two levels by themselves.
I mentioned in my last post that I was allotting my talent points to take advantage of cat form, as I already knew I'd be spending most of my time in it. But there is considerable disagreement as to which specific talents to take. A lot of people will tell you to get to Omen of Clarity in the Resto tree first, because it's multi-use. It'll help you in Cat and Bear form, and if you intend to do any serious tanking that might be a good idea to pursue. However for me I know that I won't be tanking regularly and will be spending the majority of my time in Cat form running quests. Therefore I think the best plan for me is to get Feral Swiftness in the Feral tree first, then continue working down the tree until I can pick up Mangle at level 50. I already know that once I get Mangle I'll never use Claw again, so after picking up Mangle I'll go back and work toward Omen of Clarity. Chances are I may want to start tanking again as I hit the Outlands, so having it by that point will come in handy.
On hitting level 20 you also get a mount. Which, frankly, is one of the best things since sliced bread. Even with travel form you can't help but do the Snoopy Dance. Makes the considerable amount of travel you are doing by this point much easier. Especially if you are like me, and realize you can get faster XP by working two zones at the same time. Bounce back and forth between the Crossroads and the Ghostlands for plenty of green quests.