Does speed get slower with more people?

Hi,

I don't own Fios...yet. A salesman claimed that with Comcast, the wifi speed gets slower the more people get on, but with Fios, it doesn't.

Is that true?

I never noticed a slow speed with Comcast before now. But lately any time after 9, pages take 15 seconds to load and I'm about to throw my computer out the window. If Fios really is fast all the time, I'd consider switching.

Any comments from existing customers?

TIA.