I've never found any that don't work, but Firefox supports fewer "standards", so you can end up with a somewhat degraded experience on some sites. My own company's product, for example, has some janky bits on browsers other than Chrome. The performance is only a little bit behind on most benchmarks, but isn't anywhere near as fast for certain kinds of animation. It can be noticeable on sites that run a lot of animation. Like, say, sites with ads. Possibly only if you're using an older or less powerful computer. Which isn't how we of the orange header bar like to roll, but also isn't a terribly uncommon thing to do out there in the wider world.

(Scare quotes around "standards" because calling Chrome-only things standard nowadays seems a bit like calling AcitveX a standard 20 years ago.)