Re: Grrr - so far I've been really happy with my G3
On my stock unlocked G3 (software version V21a-EUR-XX), I can add and remove Smart Notice just like any other widget. Are you referring to the full-page Smart Bulletin instead? You can remove that from Settings->Display->HomeScreen.
But, like you, I can't see the Smart Notice update in the "Update Center". It's not helping that there is no "Check Now"/"Refresh" button in the App Updates panel, so all I can do is set it to check daily and wait.
My experience with Cyanogenmod (on Galaxy S2) is that it's great for scratching a nerdy itch and getting the latest Android fixes and features (continuing long after the OEM has stopped providing them) but bad for stability. Things may have changed since I tried it but, judging by a quick look at the G3 CM forums, they haven't changed much.