I run them on almost all of my pistols. The comment above on the front dot being to big is from someone who didn't read the directions on how to use them. At ranges close enough for the dot to cover something you aim off of the top edge of the dot, you do not cover your target with the dot like a traditional sight. It takes a little practice but they are well worth the trouble to learn. Besides they're not designed for precision target shooting, they're tactical sights. If you use them the way they're designed they're the best sight on the market IMO. Obviously they're doing something right since Trijicon is now basically copying them in they're new model. I like the look of the Trijicon since they offer different colors but haven't tried any yet. I think the best application for the big dots is the front sight only for J-Frames or other snubbies. I've got 2 wit them and love them.
As for the OP's other question XS does install, usually with about a 1 week turnaround and does it free most of the time. If it's a J-Frame with a staked front they charge $8 to drill the hole (I did my own) or like $75 to cut down the fixed front blade and mill in their sight on older J-Frames.
As far as them not being bright I guess they have duds like everybody else. Over the years I've used night sights from basically every brand on the market, Trijicon, Meprolight, Tru-Glo etc. and the XS are as bright or brighter than any set I've ever used.