Have you guys messed with the beta versions of Wireless Tether for Root Users? (
android-wifi-tether - Wireless Tether for Root Users - Google Project Hosting) I removed the market version and installed the beta download from their google site (after removing the included version, I wiped cache from recovery before installing the beta). After playing with some settings (device profile - auto, even though there's an optimus S option!, setup-method - Netd (master)), I connected to it from my laptop, and it appeared to be in infrastructure mode (not ad-hoc!), based on the Windows 7 icon in the wireless AP list

I also connected to it from my wife's HTC Hero, and it works!
Unfortunately, it reboots when you disable the tether... so that's rather frustrating.
Anyways, I assume you guys have seen this already, but I pulled all this info from the Nexus S 4G forums (which is coming tomorrow - woo!), here:
http://forums.androidcentral.com/sp...-using-android-wifi-tether-3g-4g-2-3-7-a.html
Hope this can help someone and move things forward!