Electrolysis (multi-process Firefox) is now enabled by default in Firefox Nightly (v39), and is being targeted for stable release later this year.

Currently, Vimperator does not work at all with e10s. A few examples of the bugs which render it unusable in Firefox 39 include:

• The settings (liberator://help/options) cannot be opened at all when e10s is enabled
• Insert mode is broken - clicking inside an input field does nothing, which means all input is essentially broken (I am writing this comment with e10s disabled).
• Find (/) is broken

I'm filing this ticket as I've been a longtime user of Vimperator - it's a must-have extension for me - and I couldn't find any other reference to e10s on the issue tracker except in a comment on an unrelated issue (#87).