You guys are kind of leaving out an important feature though.
You can also mentor people in your group.
For example, if I (41 Paladin) want to group with my buddy who just started and is a level 6 shaman, I just group with him and mentor him. Poof, I'm level 6, with all the appropriate spells and my gear properly geared to that level. I get 50% less experience for mobs that I couldn't get xp for anyway :) My buddy gets 5% extra xp for being mentored.
Personally I think its a huge feature to be able to group with anyone you want, while removing the possibility of any serious powerleveling.
Not that I have anything against PLing, I'm a big fan of it actually (as in, I found it a great deal of fun to PL my alts on another account). But SOE wanted to remove PLing and they did, but they added this other feature that I find quite useful.
Other day I'm passing through Antonica and this guy wants to kill grolven but he can't get anyone to help him. I group up with him with my pally and healer, and mentor. We kill grolven, he's thrilled, and I didn't have to stand by helplessly just because I was out of level with the guy.