I have to say I'm not overly interested in most of these online apps for professional use- except google docs, that is. First of all, paying for these services doesn't make a lot of sense especially since you can do a lot of the same things for free using other tools.
Google docs has been revolutionary for me- no more sending emails to myself and attaching new versions of a document I work on in different locations and on different computers. I have experienced some glitches with it when trying to share a document in order to collaborate with co-workers. Some participants who did not have google accounts were, for some reason or another, couldn't access the documents in question.
30 Boxes seems cool, but Google has a similar calendar that you can share with people. And since I'm already keeping a calendar on my iPhone, at work and a physicial calendar/agenda, this seems superfluous...I think I may be reaching information overload and don't see the point in signing on to yet another service, especially if you have to pay!