I'm working with YAMs and I can say that it's very powerfull. The latest version is stable and if you go deeply into YAMs you'll be able to get a full multilingual site without having to dive into the html code. (You need to think about your site structure before though).
I do every multilingual part (buttons, forms, snippets returns, links etc) using multilingual docs and YAMS snippet calls or Yams placeholders.
I am using it since years myself and I am very happy. Found and fixed the encoding issue.
Glad it now works with the latest version of Evo (1.1).
I have at least 15 sites live running with YAMS and very pleased its there.
Evolution user, I like the back-end speed and simplicity