candleJack: "it's decently built" ?! That's the first time I hear such a statement about an L. Doesn't sound too good. Or maybe the perspective was skewed by the price. :)
I think lens 'size' matters in near future. Can be a good travel and all around lens. I do have 24-105 but its size is big for personal uses.
I bet Canon considered the less MP factor before launching this. It sounds like a big 7D sensor. Have you tried 7D's highest ISO with Adobe LR3? It just was amazing. DPP failed to remove the noise at the highest expanded iso. With the noise removal of LR3, 7D can produce much better bigger size prints (up to 20x30 with no problem). I almost get rid of 7D due to noise before I used LR3. Normally I use 1dsm3 and 5dm2. When playing with 1000+ test shots with 7D and LR3, I can feel its potential of a bigger version of 7D sensor which makes the same 18MP with much better high iso performance and resolving power. I think it is a balance move by Canon considering how many want more MPs. With much better softwares for stitching and HDR with computer processing power, 20ish MP can be the max for 35mm DSLRs. It will be interesting to see how Nikon responds with D800 and D4 in terms of MPs.