The reason you level up in WoW is because you want to grow in power, is to have new abilities and have more talent points!
By increasing level cap and cutting the number of talent points in half really cancels each other out.
When I heard cataclysm was coming out I was excited for the new talent tree combinations I could make, such as having 51 point and 21 point talents at the same time and was imagining exciting situations where those could lead me in.
Except that now Blizzard decided to kill those dreams.
For christ's sake just leave level cap at 80 and give players who buy the expansion 5 new abilities and it is the same if you were leveling or not.