I bit the bullet and updated my iPhone firmware to 1.1.3 today. Luckily, it all worked out: it's still a phone that works with Rogers, and I've got my own icons back on there (including the new iTunes icon I did this past week.)
Before I updated I was running firmware v1.1.1, with unlocked baseband 4.01.13_G. Since I bought my phone back in August, that means I was still on bootloader 3.9.
Starting with an activated, jailbroken & unlocked phone (without removing the hacks, essentially), I followed these instructions to a T (except I used ZiPhone 2.4, and stopped after Step E), and it all worked. Even the new map locator works as expected.
I did have to re-install the "non-legit" third party apps, but I didn't have to re-sync all my music and photos over; since iTunes handled the phone update, it was all there waiting for me. Nice. A far cry from the past "Option + Restore" update methods.
(None of the screenshot tools I'm aware of work with 1.1.3 yet however, so you get a photo instead of a direct screenshot)