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.