I've been solo running the story on Normal mode off and on since yesterday and I'm currently LV 31 (almost at end of Act 3). In my opinion, its much more fun than just getting power leveled, and it forces you to learn how to play the game AND gets you good gear as you level up, rather than rushing to cap with NO gear. lol.. Maybe I'm wrong, but I still like doing it myself and actually having the time to experience the storyline. ^^
EDIT: Just saw a LV 48 Wizard in chat and decided to inspect them. They're still using LV 26/36 gear. Obviously they got power leveled.. lol..
PS: How will Loot 2.0 work for those of us without the Reaper of Souls Expansion once it comes out? Will some of those changes affect everyone?