[dagw]

I often mix the two languages in a single sentence

This, for me, is the killer feature of SwiftKey. I hate having to go into some settings panel and switch between languages each time I want to type something. I don't think I'd ever consider switching to a keyboard that didn't support this.

[brcrth]

I use 2 languages with the stock 4.2 keyboard just fine. Changing via spacebar.