I have a 2Mb connection and I find Speedtest whooshes up to 3 / 4 Mb when the test starts, then it drops to 1.5, before settling at just over 2!
You can test to other parts of the world (including random places in deepest, darkest South America!) but these are generally slower than the test servers in the UK.
I find the best way to gauge true download speed is to watch the "received bytes" counter on the properties dialog box of your LAN / WLAN connection. Put simply, bigger jumps in the counter when you're downloading mean a faster speed.