Well, multi-column was started like…. more than 2 years ago by Sean at an iPhoneWebDev hackathon.
As far as i remember, a lot of work was still needed on that.
Since iUI makes all sliding navigations based on hash value, having multi-column is very complicated and need some complete refund of the core functions.
I was waiting for v0.5 to try something like splitting hash value with "-" and target different panels.
A lot of work. It needs to deal with browser history & integrating ajax loaded external panels sounds like mad to think of.
If a skilled Javascript developer wants to work on it, i'd be happy to help, but i have no time to do it by myself atm.
Remi