Where can I get new Aegisub? Ubuntu reps have only 2.1.9 which is VERY buggy (it doesn't support cyrillic lower case, it's unaceptable for me). I found only source, but I'm not sure, that I can do everything right. Where to get new package (at least newer)?
You have two options: compile from source (which is easy if you follow the instructions) or use a precompiled package for 12.04 with your 12.10 version. In both cases you will get
Install from precompiled package
On this page someone provides precompiled packages of aegisub and wxWidgets (install both packages) for Ubuntu 12.04. Despite the warning that the package is of low quality, the installation should work with Ubuntu 12.10 as well.
Compile from source
I've found step by step instructions in the aegisub forum. Please take a look at the post, the poster explains all steps.
A short version in case the link goes down: