Long story short: I'm amazed at how useful 24-105 is on FF. With 8 L lenses and cameras in three different crop factors here, I now find myself debating what to take for simple stuff, and 24-105 on FF is often a reasonable one-lens solution.

I started with a 1D Mark III and 24-105, and three years later got the 24-70/2.8 (the 24-105 went to my wife's bag, and her kit 28-135 has been on the shelf almost completely since then). Now that we added a 5D Mark III (it's "hers"), I often grab the 5D3 and 24-105 for the simple things.

That said, if the price increase to include the 24-105 is $600, don't get any dreams of selling it for retail (in my opinion). Canon has basically said it's worth $600, so if you want to put it on Craigslist for $775, don't hold your breath.