There are several threads already in the forum which discuss proper optimization of your connection. By default, the settings in Windows are not optimized for higher speed broadband connections and need some tweaking. Search around the forums here a bit.
Also, in the case of SpeedTest, be aware that several of the "test" sites don't deliver the full throughput possible by some broadband connections (unless you're talking the Verizon sponsored speedtest location) -- for example, my default site which comes out of Virginia somewhere consistently gives me 30/15 results. However changing to a few different test servers will give me results which return values much closer to by 35/35 service.
This is very timely for me. I just checked my download & upload speeds using http://speedtest.verizon.net and then used the Optimizer for Macs and here are my results: download—23.79mbps; upload—2.464mbps. That is AWFUL and I'm paying for 25/15!!! My Mac OS X (10.6.4) is using a wired connection to my router and I'm running Safari for my browser. Any help much appreciated!!!