I wouldn't trust speedtest farther than I can throw it. After having performed several very scientific studies, I can confidently say that my unbiased, normal download speed is about a tenth of what speedtest claims it to be. Apparently the ISPs put speedtest's connections on special priority. Furthermore, as soon as my connection hits a speedtest server, my connection speed overall markedly improves for an hour or so, resulting in download rates fully seven times normal (note this is still less than what speedtest claims).

I am currently using this to my advantage with a cronjob that requests a few kb from a speedtest server every 30 minutes so that I never leave the ``customer who is irritated with their speed and might just be about to switch to the other side of the local duopoly, so we'd better give them something within an order of magnitude of what they pay for'' pool.