I used to be a big fan of Foundation but they kind of lost me, everything changed a lot and I don't really know where they are at now. What I know is that the default design is ugly and that's why I keep using bootstrap for my projects.

I can say I have a positive experience with semantic since I'm only using that now. But I'm very lost and it feels like it could take a long time to learn. Although you can start using it the same as you use bootstrap, include the css and js as CDN and here you go.

I used semantic-ui for a very short period of time before moving back to bootstrap (needed to support ie8). My impression was that it is very hard to overwrite semantic classes (selectors are too specific), and components don't play that well together, especially if you're modifying some of them.

it doesn't look like it is the semantic way. You are supposed to theme everything and then compile.