So far, I've only had one experience with dropbox, and it was mediocre. Someone('s dad) was trying to share a ~1.5 gig file with up to 50ish people (mostly artists and musicians). The free account used up all its bandwidth and the person had to apologize to everyone and ask that they please wait while they figured out what to do (I assume they were using a free version and needed to upgrade, but that's just a guess. The Dropbox faq doesn't say anything about bandwidth).
So I uploaded it to amazon s3 and configured direct access to the bucket via the web (a very easy procedure though somewhat technical). It cost me less than $5 to get that file to the remaining people, with little worry about service interruption.
See that really isn't the main use case for dropbox, dropbox is more like seemless backup and sync.
You have a dropbox folder on your computer you work on stuff in, everything gets uploaded and revisioned while you are saving files and when you change computers everything is there.
You also get pretty good folder sharing with others and a web interface.
Personally though I've stopped paying for dropbox and might consider going back if they implement client side encryption for some users, but til then its waiting for a fast enough good enough replacement or for dropbox to implement it.
So I uploaded it to amazon s3 and configured direct access to the bucket via the web (a very easy procedure though somewhat technical). It cost me less than $5 to get that file to the remaining people, with little worry about service interruption.