If you have an Escort 8500, do not, I repeat, DO NOT purchase this detector. Sure, it's wireless. Sure, it runs on batteries. Sure, the display is off until a warning sounds. But the damn thing eats up batteries like fat kid on twinkies. I ran through 2 sets of decent Duracell AA's in TWO days!! Even after powering it off manually after each trip! What a joke! Stick with a wired detector. The S2 has a plug-in jack on the side, and if you really want the S2, wire it up. Also, there's no difference when it comes to sensitivity between the S2 and the 8500.
Two other gripes: 1. During the day time the LCD display gets somewhat hard to read. Night-time reading is very good, however. 2. Unlike the 8500, the display faces directly forward and not angled toward the driver. It seems a little nit-picky, but it's a nice feature that I like on the 8500.
I ended up returning the S2 and wasting $50 on a restocking fee, so to save all of you $50, I'm telling all of you now, the 8500 is your best bet.