If you are thinking about whether to take your data into the cloud, using Xmarks should help you gain more insight through personal experience.
Depending on how you set things up, you'll be wondering what the fuss is all about with Xmarks, or marveling on why you had not used it sooner. I'm among the fans, but it's not of the `diehard' category. Last month, my 6 months old laptop suffered a failed hard disk. It's quite exasperating having to set things up again. I'm thankful I had the foresight to backup some things online - with Xmarks, I got back my bookmarks immediately. It's very useful, it's great, but Xmarks isn't `a killer add-on'.