From what I have read there are a few distinct advantages to the 600.
You forgot to mention the 200mm reflector which should save you lots of battery juice if you use tele fill flash. While maybe not an engineering innovation like the rt upgrade this will be very handy for me when shooting outdoors against the sun.
But there are also quite a few negatives too.
Um, like what? Size? Price (which of course is rather steep, after all it's just a flash)?
In fact, now that the 580EX II is officially discontinued and no longer appears on the official Canon website in their Speedlite product lineup, some retailers are actually charging a 'premium' for the older model
That's what I saw, too - so if I'd want a 580ex2, I'd get it used. Or wait until the 430ex2 successor is here and the price of the "old" infrared equipment plummets further.
The question is when and if Canon will release rt addons for legacy flashes, and how expensive they'll be.