One thing I didn't like about the install was it wanted me to drill a half inch hole in the back of the column. I'm not a huge fan of putting holes in my column. Instead, I grabbed a piece of 1.5" UHMW tube left over from another project, cut it down to 5 inches long, and then squeezed it into an oval cross section using my bench vise and heat gun. I then drilled a 8mm hole through it 4.5" from the end. One end of the gas spring is bolted through using the hole, and it's then lowered down onto the column. The UHMW tube then site on the mill's base inside the column and spaces the gas spring correctly. This way there's one less hole in my column.
On a related note, UHMW is a horrible plastic to machine. Use something else unless it's absolutely necessary.
Ultimately, I think for the money this upgrade is worth it. It's not a huge difference, but it makes the mill nicer to use and definitely made mounting the Z axis DRO much easier. It also doesn't stick up above the mill as high as I thought it would. From the picture you can see it only sits a couple inches above the motor.