If you want to see one working, head out to Manchester airport aviation viewing park, there is one on display working showing live aircraft movments. It's at the Burger van, i saw this working there 18 months ago & got myself one.
I got mine from here;
SBS-1e Virtual Radar
These do next day delivery.
Seems to have gone up in price a bit though, mine was £385.00 this time last year.
Just had a look around at other dealers & they are all selling them at £449.95 even on E-bay.
Cheers Trev