Well, the thing with MoP is there is infinitely more things to do at level 90 outside of simply gearing up, and, especially true in this patch there are multiple ways to gear up a character (real raiding, LFR, questing, heroic scenarios/daily challenge mode dungeon) but the 5 man model used in wrath and cata has been totally gutted. We are 3 patches into the expansion (with the 4th supposedly going to PTR soon) and the only thing you can spend JP on is blue gear that is literally almost 100 ilvls lower than the current best (upgraded) gear in the game, and it's the stuff that has been there since launch.
So it's either that low-ilvl blue gear or heirlooms for JP? Well that's...interesting. Still, whatever it takes to gear up my characters, that's what I'll do. I only used the "chain run 5-mans" method because it was the path of least resistance at that point in time. Scenarios sound really interesting, and I'm looking forward to trying them out. Also looking forward to all the level 90 content I've heard about. The hard part is deciding which of my characters I want to take to 90 first, since I have four 85s all waiting for it.