I'll be ordering my RB in the next few days.. but if it's anything like the SBS-1 (in fact I believe it's a bit better from what I heard), you should be able to pick something up pretty easily, unless of course, you're no where near aircraft or an airport.
I'm in Sydney Australia and own an SBS-1 and I pick up aircraft up to around 35nm for low altitude aircraft, and 185nm for high altitude aircraft from my living room in an apartment building which is surrounded by other buildings using the stock mag mount antenna. Admittedly, the positions are lost often so I can't track for long periods of time, but considering how little sky I can see from my veranda and my antenna is in my unit, not outside (it sees no sky), I think it does remarkably well.
Incidently, I'm about 20nm from the airport, live near the bottom of the apartment building and the flight path is on the opposite side of the building. When I last did a polar graph, I found I picked up more on the other side of the airport rather than what's physically visible and close which is kinda weird.
I'm rather looking forward to getting the RB simply for the color maps, and alerts functionality. Both sadly missing in the Basestation software for the SBS-1. Still like the SBS-1 for other things, but RB has huge potential if they continue to update the software with improvements especially if they did things like allow more customization of aircraft data on the radar screen itself. The more you can customize about what you see, the better this product will be..
I think you'll enjoy the RB (even though I'm using the SBS-1 at present, i've played with the software to get an idea if it's worth buying, and i've decided to go for it. Just got to wait a few days to buy from my dealer here.)
Geoff