Simply speaking, yes you may see the 100mbit/s but that would be local servers. most off the shelf items can support those speeds. But that would largely depend on the amount of traffic your ISP is handling at that point in time, the server load that you're loading content from & physical distance from you to the destination server.
If you do a speedtest using a Singapore test point, chances are that you'll easily hit the max advertised speed. try to do it using a China server and you'll see the difference.
The main difference between fiber & cable is the upload speeds as uploading is nerfed by the ISP most of the time. What I was talking about in my post is needs vs wants. I need internet that is reasonably fast enough to surf the net and the occasional flash games. I don't need my internet to download at greased lightning speeds.
Most importantly, I hate it when sales people try to hard sell me something when they don't know anything outside the brochure
