This lens has probably caused more soul searching and cost justification than any other in recent Canon history. Can I justify spending this much on a lens whose range I can duplicate with lenses by 3rd party manufacturers I asked myself.
To that end I sought out a vendor who specifically said that 7 days approval was fine by them and so I ordered it. I didn't need the 7 days - after the first day I knew it was a keeper. I spent the day giving it hard jobs at a Triathlon which was being swum/cycled and run on a dull, overcast day which needed a fast-ish lens which focussed first time, every time.
Towards the end of the day the sun broke through and I was able to shoot directly into it [without the much sought after, scarce and infamous 83J hood] for some West Coast beach scene sunsets [lots of glare and reflections].
It behaved impeccably on my 30D and replaces my 30mm f1.4 and my 60mm f2.8 [both very sharp] which were my walk round lenses. All the usual parameters - sharpness, bokeh etc etc - have been previously described and I won't bore you by repeating their various merits. One thing I shall point out though, and which has been missing from previous posts, will amuse the Full Frame users reading this.
It's the sheer convenience of having a sharp [equivalent] 27-88mm f2.8 zoom for the first time since I went digital. All the 28-70 f2.8L full frame users will know what I'm talking about if they think about it for a moment. Having the above with IS is just sheer luxury.
If you have doubts about the cost of the lens then that's your prerogative. If you have doubts about the value of the lens then go get one on 7 days approval. But be careful - it might make up your mind.