The BCS plugin, like PDF Reader or Go-To-Meeting, provides a powerful and, crucially, accurate platform for connection testing.
There are many so called "Speed Tests" out there today but the reality is they are not accurate. Browser only tests that do not require a plugin are simply not capable of performing tests like VoIP, Route or Capacity.
In short, they do not measure the true user experience of the Internet. Visualware BCS does.