I haven't tested the CS B-52 radar at low altitude, but with a real radar you will have shadowing (Black areas showing no return) behind terrain higher than you.  If you see shadowing in front of you, and you continue on that course, you will hit the terrain.  I am not sure if the CS B-52 models this.  Also, real world ground mapping radars will paint both ground as well as air targets.  As a matter of fact you can use radar in IMC conditions to align yourself with a tanker.

 If the sim doesn't show shadowing, fly low level and refrence a chart for terrain altitudes.  You can then use the CS radar to scan for terrain features in your area.

I am pretty happy that CS took the time to put this feature in the sim.  While it would be pretty awesome to have more real world radar features, I am not sure how easy it would be (if even possible) to model them in FSX.  Also, I am not entirely certain most users would even care to use these features as it would require study time to take advantage of them.