Well as long as you can still root the phone, you are halfway there.
If you can, try your best to get Recovery (I'm using ClockworkMod) in there so you can always load the ROMs (standard or customized) to your own liking.
*remember to wipe all the data residue from the different caches*
I normally use adb on the command line but I'm still reliant on having shitdows (I'm using XP) to detect my HTC Desire Z. As you've mentioned Terminal on Mac or any Linux variation, is actually the easier method in my humble opinion.
Here are some links: (my bad for not including them in my first post)
http://techie-buzz.com/mobile-news/comp ... xus-s.htmlhttp://jaxov.com/2011/02/how-to-root-an ... n-nexus-s/Give it a shot and good luck!
ICS 4.0 isn't shunned by all. The peeps who prefer ICS on their phones running everything standard and legit (without all the hacking and customization jazz). Usually, clueless users that actually pay for apps. The GUI and menus look all pretty but to a hacker/developer most of the cool apks have not been ported to ICS.