I'd also like to point out that you can get 3 yn568s (released soon) and four yn622s for about $650. This is full ettl wireless, manual, ratio, mixed mode, hss, built-in bounce cards. In fact the only thing that the yn568s can't do is support a battery pack. Admittedly, for some people this is huge, but for many it's a non-issue.
Now do the math for 3 600exs and the new trigger (which doesn't have an assist beam, and will not support 3rd party flashes, or most canon flashes).
For "pros" who do heavy strobe work, then sure, they might want to get the canons. They will probably last a little longer, and be more reliable, and they can put battery packs in them.
For "pros" who do mild flash work, this is a dream setup. Also, I've heard nothing but good reviews an the yn622s. I know the old yn565s had terrible issues, but that was fixed, and I'd imagine that the 568s will be built to last also.
I have a 560, and unless I need ettl, I use it before my 430exii. It has an optical trigger, is more powerful, has a built in bounce card, and is much quicker to operate because of the smile menu. It hasn't misfired once in over a year of mild use.