Chrome has a nice feature where you can see what tabs you have open on other computers (assuming you are signed in and have sync enabled). I think Firefox has the same, but I don't use it often enough to have looked for it.
I'll point out the obvious, which is that now your bookmarks are all tied to that browser. Not a huge deal if you don't want to switch browsers any time soon, but it can be nice to sit down at another person's computer and pull things up.
Manual import/export isn't really a useful option when you are using multiple browsers on multiple machines, let alone sometimes wanting to access things on public machines.
You were also, at that point, restricted to arbitrary hierarchies rather than arbitrary tagging. The ability to slice bookmarks over multiple categories is stupidly useful (for me anyway.)
And even if you don't want to use the Chrome sync, there's services like Xmarks (which is available for both Chrome and Firefox, and you can also access your bookmarks via a website, and make all or part of them accessible via RSS)
Chrome has a nice feature where you can see what tabs you have open on other computers (assuming you are signed in and have sync enabled). I think Firefox has the same, but I don't use it often enough to have looked for it.