Earlier this year I moved to a Canon 5DII (I also bought a Rebel t3i as back-up) from a Pentax K-5 (which supposedly has a better sensor than the 7D) after renting 5DII + 24-105 and doing some direct comparisons. If you can do the same, I would recommend it, as we all have different needs/uses and standards; the differences that matter to me may not matter to you.
Among other differences that matter to me, the FF is much better at capturing busy detail (e.g. leaves on trees), cropping is better, shallow depth of focus is more easily obtained, and most important of all, images in low light (typically outdoors; I like cities at night) look far superior. On the other hand, there are situations where the differences are minimal to non-existent (simple subjects in bright light that are fairly close, for instance). The failures of the 5DII's autofocus are lost on me as I hardly ever want to shoot something that moves fast.
As others have pointed out, f/4 on FF is at least as good as f/2.8 on crop in low light, so you can imagine just how much benefit you can get with faster lenses on FF - I'm often amazed at how low the ISO can get in relatively low light with even f/2.8 (let alone f/1.4). Throw in effective IS and the situation only improves (there are situations where a slow lens with IS yields better results than faster lens without IS).
As for the poor corner performance of the 17-40, all I can say is that I almost never take a photo where something in a corner should be in focus (the reverse, in fact), so I don't care. It's certainly true that the huge barrel distortion of the 24-105 at 24 will look worse on FF, but if you have software that fixes that sort of thing (I use DxO, which does so automatically) it doesn't matter. As for complaints about these two lenses cf the two EF-S lenses you have, perhaps I've been lucky with my two or unlucky with the 17-55 I rented (I've not tried the 10-20), but I much prefer the results I get on my 5DII with the 24-105 than I did with the 17-55 on my Rebel, which was at its best on close objects. (I also think that people around here exaggerate the differences among good lenses, but that's another matter....)
So, I would suggest you rent or borrow a 5DII/24-105 combination (or 70-200 f/4IS, for that matter) and compare it with your 7D + EF-S lenses (and compare the rented/borrowed lens(es) on both). You may reach completely different conclusions from mine....