Loren, that sounds really strange. I know Dropbox has millions of users and I've heard many, many testimonials from people who find it works flawlessly.
The only time I've ever encountered a problem like what you describe is if I've added a large item to my Dropbox folder and then shutdown the computer before the file(s) finished synchronizing with the Dropbox server. In that case, I checked another computer and was surprised to find the files didn't come through, though of course they came through later, after I turned the first computer back on again and the files uploaded.
Are you sure it's not something like that? Also, if you log into your dropbox account via their website you can see an event log that shows files being uploaded, deleted, changed, synchronized and so on. You should be able to see there at which stage something went wrong. I've used this on maybe two dozen computer and an iPad and have never experienced the kind of problem you describe, except in the instance mentioned above, which was my own fault. I now make sure I don't slam my laptop shut (which puts it to sleep) just after I've added large items to the Dropbox.