Ready to update your Samsung Nexus S 4G to GRJ90, but don't want to roll back and lose root? No problem -- Shabbypenguin has you covered with a ClockworkMod flashable version, all ready to go. It's pre-rooted (of course), deodexed, and has busybox tossed in, but other than that it's the stock system clean and shiny just like you would have had you accepted the OTA. Of course, there's that small matter of native tethering being broken to consider, but it looks like the easy way to go. Hit the source link for more info and downloads, and be sure to thank Shabby!
Source: Android Central forums