The latest stable version of ansiesc in portage doesn't support properly the esc sequences used in the portage log files. The latest cutting edge version of ansiesc available in the author's webpage (http://www.drchip.org/astronaut/vim/index.html#ANSIESC) fixes the problems making possible to read portage log files with vim. I'd ask to add a snapshot of ansiesc to portage to improve reading of log files with vim.
