I've started using Dropbox but I'm finding that my upload speeds are dropping down to the withering pace of 6Kb per second. I have checked my upload speed with speedtest.net and I get just under 1Mbs.
Is this due to preferences or settings on my install or would this be something out of my control and related to location or ISP?
Check your Preferences. By default, Dropbox doesn't limit download speed, but limits upload speed to whatever they think is sufficient.
I don't think it's a problem with Dropbox but your Internet connection.
Usually the upload speed of your connection is slower than your download speed, using a site like SpeedTest.net will show you both values and if you can publish them we can have a better idea of what's happening.
It would make sense also to take speed tests at different times for comparison and to know if your ISP is overselling the channel and is not delivering the same speed all the time.
But if your upload speed is slow there is not much that Dropbox can do about it.
It's my experience also, so I moved to Wuala.
From my experience Dropbox seems to slow down the speed when you have a lot of files to download (f.e. when you have a new PC that has to download the complete storage once). F.e. when I have to sync only 2-3 files then I get "normal" speeds of 700-800Kb/s. If the number of files to download are f.e. 30.000 then it's slows down to 10-60Kb/s.
So it seems like Dropbox is saying "oh you have to download a lot, let's bring down your speed otherwise our server will be tired ..."
The up/down speeds depend on many different variables. Please see Why is my internet so slow? for detailed explanations.
As for your question, it's not a common experience. I just tested a 5 mb file and it uploaded just fine, i.e. using the full upload bandwidth.
You can also check status of Dropbox to see if there's any current problems with servers, locations, app etc.
