my friend has a decent one, but I forget which. Its pretty cool because it says the strength, and around me they still use ones that take a few seconds to "lock in" so when its just on 1 bar, you should start braking, but as long as your are only doing 10 over by the time it gets to 2 or 3 you will be fine (4 to 5 is considered "locked in" usually). Around where I live, you don't really need one, usually pretty easy to tell where the cops are/will be, but definitely cool if you just feel like cruising.
As far as legality, around me they are legal, as long as you use a stand. you can't have them with suction cups on your windshield because of laws about obstructing the view. Also, make sure you talk to people who live near you and know what the cops are using for radar/laser guns. This can make a big difference. Also, if you have the money and it is legal, laser jammers are supposed to work very well, can buy you a few extra seconds. A lot of the stuff may seem expensive, but its worth it if it stops you from getting pulled over as it will save you from getting a ticket and possibly loosing your license. Lastly, don't be an idiot, don't speed near schools/in residential areas. Many times you can get called in if people see you doing something stupid, and then it really doesn't matter what kind of set up you have.