@frankensteiner Hi Frank, I have been using RWML on http://www.bensaglobaltrading.com and must say it works great . Apart of the content, menus, etc the slogan under the title is translated too. There was some issue that I din’t find how to translate the slogan under the title because there isn’t a RWML stack option to do so but Joost the developer of RWML have sorted it out and have send me a personalised snippet to put into the Settings>General>Slogan of my theme.
RW haven’t behave slow with the two languages on one stacks-pack, just working fine to me. RWML is a great stack if you need a multi-lingual website and must say the client support of RWML, Joost the developer, is top … just drop him an email and he will sort it out for sure.