I have roughly a dozen sites I go to. Most of them happen to have different first characters, so I type "f" and Chrome autocompletes http://fark.com/ and off I go. No bookmarks other than the shared history Google keeps for me.
I haven't used the built-in bookmarks feature for years. I checked just now, and I have 10 bookmarks stored (all of them used for quick searching in FF). I still use the concept though, I just offload them to Delicious where they can be properly tagged and shared.
Looks great, but I'm happy with what I have now so I'm not too pushed about spending money on a service. I'm also old enough to worry about trusting a site to hang around for 10 years with my data. (and by old enough, read: stuck in my ways enough) Must look into the migration effort though. And browser addon support. Its definitely a sweet looking service.
If you go for the premium service, a bargain $25 a month you get the ability to have it scrape and download every site you bookmark. So even if the site you bookmarked goes down, you retain the content.
Pinboard also has good APIs so you can backup your data. No lock-in.
I'd say I do too, even for stuff I have bookmarked. In fact 80% of my bookmarks provide nothing other than peace of mind for a person with a terrible memory. :)