Pros:
the LED is bright enough that I don't need to use the reflective sticker.
the unit pick up GPS fast and is extremely responsive and accurate UNDER 40 mph.

Cons:
there's a offset when your speed goes over 40 mph
@ 40mph the unit shows 42 mph +2 mph
@ 50mph the unit display 53 mph +3 mph
@ 60 ~ 65 mph the unit display +5 mph.
cross checked with phone's gps mph.
Good thing is that the 2 ~ 5 mph seems to be consistent.

Works fine

Last week I got my one and it’s really great product and I’m really happy that I got it.

Love it. My 1970 car speedo broke and is a major pain to just get the instrument panel out much less repair it so i looked for a solution besides using my smart phone and found this. Im totally blown away at how great this thing is. I used the film that makes it very visible but u might not need to depending on your particular glass in your car. After trying it out i made it more of a permanent installation by semi hiding the one power wire by running down the left side and tucking behind some trim and hooking a usb plug into the accessory fuse circuit. Only negative is as others have stated it takes a little time to get going after starting but by the time I'm backed out of the garage and getting up to speed it's good. I love having a digital speed ever since i got our regular car that has one in the dash. If i ever get around to fixing the old speedo I'm still keeping this.

I got this for my big truck. The speedometer is off by about 5 mph due to its lifted status and non stock tires. It was much cheaper to get this than take it in to calibrate my tire sensors.
Mounts easily, works well, large numbers which are easy to read.