CD,
I bought one of these early in the year to put a bunch of rounds through to see how it would hold up. It has done really well so far, with a few hundred rounds of buck and a similar number of birdshot. I also fired about 5 slugs through it at one point.
Tritium might be a bit much for your gun.. keep in mind that you have to have enough light to be able to identify the threat that should give you enough contrast to see a larger front bead without needing the glow. If you want "brighter" anyway, you might look at one of the fiber optic type front sights or a larger white replacement bead.
Make sure that the stock is short enough for your wife to shoot comfortably. The Knoxx is great for repeated shooting in a training environment, but not going to be as important during the critical incident. Fit is a better place to focus for intuitive use during a fight.
-RJP