I am a user of GoogleDocs. I started using it at work when I discovered that one of the computers I sometimes worked at wouldn't read my thumbdrive. So, I used it to access text docs I was working on. Later, I started to use it for personal uses as well . . . I have my novel I am working on on GoogleDocs (wish I would have done this previously - since I have a 65 page novel stuck on a hard drive that is waiting to be resuscitated).
The main benefit of joining a web os is also it's drawback - your information is accessible anywhere. Of course you have to know the id and password....but there is always some tech evil genius out there...so I don't know how safe I'd feel having such unlimited access to all my information if they are able to hack the cloud.
GoogleDocs is really the best solution for me at this time. I use Google. It's not like some of the services I've signed up for and then absolutely forget that I signed up for it because I never use it beyond the trial period.