Well the web shield shouldn’t have any impact if what you are downloading it considered infected or the site itself is considered infected.

I have a 40Mbps broadband subscription and checking on speedtest.net shows a download speed in the order of 37Mbps, which is close to my maximum. Just checked mine whilst doing this.

What would be a more realistic test would be to download a large file (something like XP SP3 download that is about 316MB) and the time taken for that.