In response to post about issues with the difficulty of leveling a rogue, we also got information about the some of Cataclysm's overall leveling improvements from Ghostcralwer (World of Warcraft Lead Systems Designer).

Ghostcrawler 1. The gain is every level. You don't have to reach certain milestones for your Shadow Bolt damage to increase. One of the scaling problems we have currently is that any spell without a level 80 rank starts to fall behind. Imagine Shadow Bolt just has 85 (free and automatic) ranks.

2. We changed the level at which you get abilities, in some cases dramatically. Currently, you get showered with abilities at low level, many of which aren't even useful when soloing. By sliding these around we have every class to where you get an ability about every odd level. There are still some dry spells for some classes, but then you have talents and other things that fill in some blanks.

3. Related, the spell book tells you at what level you will get future abilities so you can plan accordingly. In addition, when you ding, the UI tells you not only about newly available spells, but also systems and mechanics not tied to your class trainer, such as the ability to train riding, dual spec or use Dungeon Finder. It's pretty sweet. Our UI team is kicking some major booty for Cataclysm. 

This should be a little bit more informative and much more immediate than the mails that you occasionally receive from NPCs about new features. Hitting a new level while in the middle of questing and being able to at a quick glance find out what skills you'll be receiving if you head over to the class trainers will let you decide if you want to keep going or wait until later in the event of a skill you don't use that often.

While some will argue that this is yet another change for casuals, it's honestly a change for modern game design and keeping up with the curve. When your game is over 5 years old, there are often some basic things that need updating and the leveling process really is one of them.