Bookmarking service to replace Delicious?

I'm still using Delicious after more than 8 years but I've decided it's time to move on. So I'd like to hear recommendations for a bookmarking service that has these features:
1.Can import from Delicious
2.Has private/public option for each bookmark (so is a potential traffic source)
3.Easy integration with Firefox and/or Chrome plugin
4.Popular or growing in popularity
I've also been using Diigo, but it's no longer compatible with the latest version of Firefox.

Any suggestions?

Thanks