@wickidwombat: thanks.
So aside from ST-E3 and 600EX-RT (with radio and line-of sight wireless) there are now 3 options for light-pulse line-of-sight wireless mastering available from Canon. Each with it's own set of advantages and disadvantages:
* master-capable flash, eg. 580EX/II
functionality: master triggering, 4 channels, 3 groups (A,B,C), 1. curtain and HSS; AF-assist (both IR and flash)
Upside: powerful fully featured flash functionality; downside: bulk/weight, cost
* ST-E2 - same capabilities as 580EX/II, AF-assist (IR);
Upside: small&light, "cheap"; downside: no flash functionality on its own
* Speedlite 90EX
same as 580EX and ST-E2, but no AF-assist; basic, weak (fill) flash capability
Upside: small& light, cheap; Downside: no AF assist functionality
Plus another option available on newer EOS bodies with master-capable pop-up flash:
* 7D (3 groups of slaves), 650D (2 groups), 60D, 600D (1 group)
functionality similar to 90EX, minus HSS master capability, but plus AF-assist (flash only)
Advantage: built-in, no extra item, no extra cost; Downside: available only on newer APS-C bodies; no HSS in wireless mode
Unfortunately neither one of the "small, light & cheap" options has all desired functionality.
And regrettably none of Canon's wireless mastering options offers 2nd curtain sync whereas all of Nikons's wireless CLS options do provide 1st, 2nd curtain and HSS in wireless mode - but they got no radio wireless as of yet. ;-)