I honestly didn't know xmarks existed, I probably missed it because I used to be more of an Opera user before Chrome with only a fleeting interest in Firefox inbetween. Firefox I moved to because of Weave, and I only fully shifted to Chrome when the sync became full-featured. Xmarks may not be able to compete within a single browser, but the killer play is syncing across them.

Having just read the feature list I would happily pay $5 per month for the secure password syncing across browsers.

The bookmarks have a little value to me, but the password syncing has pretty significant value.