I'm using a Beltronics and it has saved me a ticket many times over and has paid for itself many times over in the last 3 years.
It detects Laser as well.
I find that with the instant-on types although may not help when YOU are directly targeted, does provide an indication of an area where those are being used on other folks and typically gives you enough warning of a HOT area that you could slow down in that area.
You want one that is very sensitive to detect radar/laser at the greatest range possible, so that you get enough advance warning to react.
I would not hesitate to spend $500 on a unit as it will pay for itself many times over very quickly.
Where its illegal though you will need something more stealthy than a regular radar detector, one with a passive quiet mode so it can't be detected.
The Beltronics have the anti radar detector detector technology as well.
https://www.beltronics.com/store/sti-magnum.html
Made in Canada too...eh!
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"It broke because it wants to be Upgraded

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2012 Porsche Performance Driving School - SanDiego region
2001 Boxster S, Top Speed muffler, (Fred's) Mini Morimotto Projectors, Tarret UDP,
Short Shifter, Touch Screen Dual Din Radio, 03 4 Bow glass Top (DD & Auto-X since May 17,2012)