I've got blackra1n and that's fine for breaking it after software update it applied but by applying the software update it would unbreak my phone and remove all my settings/games/apps/layout etc. I'll take a look at aptbackup and give it a bash again tonight.
incidently, is there anything new and exciting with 3.1.2?
Guy at work has found a floating version of v4 in the depths of the web and is trying to sort that at moment apparently.