The cool thing about these machines is that they're always online as the cops drive around, so whenever a call comes in, it comes to the computer in print form at the same time it comes over the radio. The big advantage I saw to this was it gave the cops the ability to study a suspect's description or confirm address details or whatever w/out the tedium and time required to talk over the radio. It also makes filing reports much easier since the cops are always with their computers and can type up reports whenever they have spare moments. Finally, cops get email all day long on their laptops, just as they would if they working an office job. I didn't see my cop send any email from his car, but he could have.
The computers also give the cops access to "wanted" posters so they can review the mug shots of the people they might be looking for. And of course cops can access all kinds of records (traffic records, arrest records, etc.) for people they stop or otherwise interact with. The cop I was riding with said this saves all kinds of time, allowing cops in the field to do nearly all the work the communications office used to do. He even called the computers "the best thing the department has done" in the 20-something years he's been on the force.
D.C. just passed a new law requiring drivers to use hands-free devices if they want to use their cell phones while driving. The idea is that people get distracted while playing w/cell phones and they should be focusing on the road. Well, if you want to talk about distraction, give drivers a computer! Many times I saw the cop I was riding along with swerving erratically, following too closely and having to stop abruptly to avoid accidents b/c he was focusing on his computer instead of the road and traffic around him. These things need hands-free devices, too! I'm surprised we haven't seen a lot of police cruisers in accidents yet. But police often drive very poorly, and perhaps one reason for that is that they're playing w/their computers instead of keeping their eyes on the road.