recoil spring laser
 

Has anyone installed one of these and or has one I am thinking about picking one up

Are you talking about a Lasermax guiderod laser?

If so, yes, I have one for my M&P9. My only issue is the activation switch is a bit too sensetive, and the batteries die quickly because it gets turned on if you just barely touch the switch.

Other than that, I like it.

how accurate is it

Well, I have a slight tremble in my hands, but when I am able to keep it stationary (like a shooting bench), it's pretty damn accurate.

Where are you getting it from and how much (presuming you do decide to get one)?

local gun shop 140 bucks

Well, if it's an actual lasermax guiderod laser, that's a really good deal (they are normally $399).