I would disagree with the IS comment, the OH bought this as she could not get on with the Non IS version, and for her it does make a big difference even at Macro distance, I would reckon probably 2 stops rather than the 4 claimed but still not too shabby for macro, at Near Macro the full 4 stops does seem nearer the mark.
She uses it on a 5d II, and on AI Servo seems to cope fine and using the IS has got her better results than on the non IS lens. I would imagine the better Focusing on the outer points of the 7D as well would help
Its just the massive price step, if you are happy with that then its a cracking lens, (But like all L it will hold value for resale)
OH has just purchased a cheap Macro Flash from Ebay to use with it, and so far the results seem very good,
I intend to borrow it next week to try out on a job that requires some very close images for court evidence so will report back then
As for prices they seem stable at the moment unlike some of the Quality glass which is going up in leaps and bounds. Not sure if there are any deals at the moment, OH purchased hers with the £75 Canon Discount voucher that came in the 5D II Boxes recently, which made it £699 - £40.83 Quidco (Jessops) - £75 Canon = £583.17 which seemed a good deal for a Brand new UK one