I've been up on the ledges 4 times now, and it's pretty well marked once you get past the crossing. I found that the bigger problem was not the exposure or climbing per se, but climbing the ledges with a full pack on. That was more of an issue with me. I got around this by bringing some rope and just hoisting or lowering the pack, and than easily climbing up or down. The climbing is pretty easy. As a matter of fact, the part that I found difficult to climb with a full pack really doesn't present much exposure. The rope I bring is just some lightweight 8mm rope. Useful for alot of things probably. I only used the rope once though, and the last couple of times through I've managed to find small granite knobs to hang onto to give me a boost at the spot I found difficult.
The north fork is harder (>6000 ft in under 4 miles vs 11 miles on the main trail), but the straight-on, slap in the face view of Whitney and the Needles, not to mention Russell, Thor ect, is worth it. Especially as the sun is coming up. And I mean worth it even if you don't get to the top of anything. You can't get that view from the Main Trail.
Oh, and the few people you meet on that trail are always a pleasure. Especially some of the regulars. quite a group.
Good Luck.