Ah. I am (was) in the same situation considering whether I should update my LT18 to ICS. I'm still on the stock GB OS and from the looks of things will be staying on it for life...
You can revert back to the stock GB but there's the issue of flashing and doing other funky stuff not suggested by the manufacturer (with the risk of bricking for the less experienced). Personally, unless it's more well-documented I won't be looking at rooting my own phone... With there being so many phones / methodologies into rooting (depending on the brand / model of phone), I won't bother learning yet. It's not like reinstalling Windows on PCs (which is straight-forward and pretty much the same for all machines).
To help with your situation though.
Have you tried doing a REPAIR via the update suite? Sure you've updated your phone through the update program. But to ensure you're phone is updated properly and fully, a REPAIR is recommended afterwards to help iron out anything that could've been missed. Doing just an update as I understand preserves your apps and existing data. But there's apparently a (likely) possibility of incompatabilities as the OS is being swapped. Hence why a REPAIR straightafterwards is recommended.
Of course, doing a REPAIR means all your existing data is erased. If you've a memory card in the phone, back it up (eg, onto desktop on your computer), and delete all the files within it (don't format it though). THEN to the repair via the update suite.
Yeah. Hope that helps. I'm an agitated Arc S user too (though that'll probably go up a scale or two once I update to ICS).
