It's worth looking at the Nissin Di-866, I bought one last week from HK, I can't really vouch for how good it is yet, but I can confirm that it has almost all the capabilities of the 580EX including master/slave operation, ETTL compatibility, multiple flash, variable power, zooming (24-105), catchight etc. The Di-866 is also firmware upgradeable via USB, so compatibility shouldn't be an issue.
I can also confirm that the Di-866 interfaces remotely as a slave with the 580EX javong tested that feature.
I haven't had time yet to do any comparison tests but I will as soon as I get back home to Tas.
The Di-866 is available for both Canon and Nikon, costs around $299 from HK, although if you're prepared to buy OS the 580EX can be had for around $450.