As far as the longest shot, yes, it is usually under 100 yards. However, there have been times marksmen have had to take a shot at 200 yards +, and unlike military snipers that usually has to be a head shot.
Yeah, there's a world of difference between military and police snipers. Military snipers have to deal with field conditions and frequently make much longer shots. However, those shots are usually non-critical. That means, if they miss, it's not a big deal. They are trained to shoot center of mass, and don't have to worry about a hostage getting killed if they mess up the shot. I've talked to one famous military sniper (I'm not going to use his name because I haven't asked his permission to) who said that he missed more than he hit, and if he did miss it wasn't a big deal. There just wasn't that much riding on the shot. If he hit, one less enemy soldier. If he missed, he probably scared the piss out of the guy and that was okay, too.
Police marksmen, however, have to train for an instantly-incapacitating head shot on someone who may be behind glass, moving, or hiding behind a hostage, at distances generally out to 100 yards. If they miss or don't get a good hit, someone else is probably going to die. And then guess who gets sued? It's a whole different ballgame than military sniping, but not necessarily an easier one.
Garand Shooter, you're not necessarily correct. You usually do have to stalk in to some degree, especially on a hostage-taker. More and more bad guys who create SWAT callouts have rifles and are entirely capable of firing back, or firing first if they see you moving into position. Sometimes they have friends who will be looking for you after you take out their buddy. Shooting mats? Not very likely, it's another thing to carry.
SS109, I'd like to have some of those $5000 super-sniper rifles. Who's buying them? Every team I've worked with has plain old Remington 700 PSS's with Leupold scopes. Some even have to settle for Savage rifles or worse.
Buzzard, stay away from the Leupold 3.5-10X police scope Remington puts on their police packages- the light transmission is horrible. Spend the extra money for the Vari-X III M1 with mil-dots, it's worth every penny. Also stay away from 700's with Remington's detachable magazine system, it's horrible. Steyr SBS tacticals are a better bet for about the same money.