The Mozilla translation extension works fine for me when I've used it. It may even be enabled by default now.
- It's slow.
- Automatic language detection rarely works.
- It only supports a few languages.
- For many sites it breaks the page.
Firefox finally sort of has it, but it's not that good. Often it won't believe you that the page is in another language, so you can't translate at all, even by trying to force it. The translations can be weird and miss parts of the page.
I'm sure it'll get better, though, and once it does, I can delete Chrome entirely.