I'd have to agree with Jeremy here. 100% best upgrade I've made to my X-Carve.
I'm not interested in photo engraving, so it's been even easier for me. Connect the two trigger wires on the laser driver to the two wires on the PWM spindle control on the front of the X-Carve power supply to trigger the laser (just flip the spindle switch to "off" here).
Single piece of angle ally to make a mount with three thumb screws to quick mount/unmount.
I do all my layout and design in Easel, output the gCode and modify that in a text editor before sending via Chilipeppr to the X-Carve and laser (change Z movements to laser on/offs).
So cutting 3mm birch plywood, cutting card/foam or marking other materials is all great. Really good at "engraving" anodised ally too. Also ablating paint from copper before etching is my main usage at the moment for use in jewellery making and PCB production.
One thing I find it really useful for is prototyping boxes/complex geometries. I can cut the design out in card on the laser in a couple of minutes (faster than with scissors and more accurate) then test assemble before applying to bigger/thicker/more expensive materials.
My neighbours are close, so running the spindle late evening is a no-no, but running the laser is fine.
Sure, it's not a replacement to a spindle, don't know of any lasers that can mill ally, copper etc. but as another "tool bit" (that's how I like to think of it) in your arsenal of tool bits, it's terrific.