You can also go to
www.dslreports.com and check out the speed tests... This will at least tell you if you're getting the download rates advertised.
When I signed up for 1.5MBPS cable service, I found I was only getting about 384kbps... Made the cable company do a line and service upgrade bcause of it.
I've never had throughput issues with WiFi... In fact most WiFi operates at speeds much higher than Cable or DSL services... So your issue is more than likely some problem with your internet config, interference (as was suggested) or some sort of tuning issue...
Check with your provider about settings. I use XP and have no throughput issues at all...