I kept the 28-135 from my 40d kit (such an odd pairing on that model) and occasionally use it on my 5d2.
The 28-135 is good in the center up to about 75mm or so, but has many flaws such as distortion and soft corners. I say the 28-135 is close to the 28-85 or 28-105. They are all near the same optically.
But I hear lots of mixed opinions on the 24-105. I know the older ones had some kind of defect that forced Canon to do a slight revision. Maybe it was flare or dust. Anyway, the market for the 24-105 is so flooded and there are some awesome deals out there on new ones from kits. Here are my current lenses: 28-135, 17-40, 35L, 50/1.8 mk 1, 70-300 IS.