Often your broadband provider offers several different deals, depending on what upload and download speed you want. If you just want to read email and look at the occasional website then it hardly maters, but for many of us, the speed of our connection is important (I care a lot, since I often work remotely from home using VNC or MS Remote Desktop, and also run a distributed backup system).
So do you get the speed advertised? Probably not; the question is how much less you get than the maximum speed advertised. Speakeasy speedtest makes it quick and easy to find out, and they print it in both the needlessly inflated bits per second, and the more meaningful kilobytes per second. Very handy!