I came in a little late to the discussion on powerjack v. escape plan, so sorry if this has been said somehow.
In TF2, almost every way you can move faster hurts you or makes you take fewer hits to die. Escape plan has the double whammy of minicrits and low hp, GRU has minicrits (definitely a nerf from when they used to do damage), explosive jumping does damage, the fast classes have lower hp... etc.
Powerjack doesn't have this downside.
On the flipside, I don't think "buff the escape plan" is any sort of solution. There's a reason the escape plan was nerfed 3x in a row yet still remains insanely popular. It doesn't need a buff.
Nerf the powerjack is more reasonable. I like the weapon, but I don't see the downside of, say, having pyro take minicrits while using it. Powerjack's a really really solid upgrade, primarily rivaled by the axetinguisher in terms of how often it's used.
That said, I love the powerjack.
On a different note, if we're talking pub play, I think QuickFix users should take knockback from airblast during the uber. Pyros with the axetinguisher are one of the easiest ways to kill a popped QF med (sans stickytrap), but knockback would be nice and balance QF a bit more. Also, if they haven't fixed it already, QF meds should be able to detonator jump with their pyros.