You can read up all you want about radar detectors but we've installed pretty much every brand out there at some point for a customer. 8/10 customers we have use Valentine1 and almost every exotic car owner (meaning money no object) uses the V1 so that says a lot in my book.
Personally my background includes working 3 years while in school for a car stereo shop that sold both Escort and K40 (the guys who pay for your tickets) and I can tell you at over $1000+ a pop back then (1998) the units sold quite well but part of the reason is we did not sell Valentine1. My take has always been if they have to pay your ticket, it means court costs, insurance goes up and more hassle which proves to me their system did not work.
I've been using V1's in all my car's for over 12+ years now and personally I own 2 units but each of our vehicles are hardwired with a custom remote display setup so I can take it to each car, connect the main unit and go. The beauty of the V1 is it works damn well on the open road capable of sniffing cops out 1-2 miles away. In the city it is too sensitive but you should not be speeding on local roads anyways so we just turn it off.
I don't want this to turn into an ad for Valentine1 since I buy them at retail price just like you guys but I really do believe in this product. I even got my mom one for X-mas.
As they say pictures are worth more than words so I'll leave you with these shots in some of my cars over the years. Not all of them are BMW's but the concept is the same, hide the main unit and put the remote display within eye level line of sight and put the remote volume unit where you can reach it near shift knob because when you are driving fast, you eyes should NEVER be looking down in the ashtray!