When I was shooting IDPA and USPSA, I used to use these sights (I liked the small dot better). I also used XS (well, back when it was Ashley) ghost ring sights on a Marlin Guide Gun and used a front tritium blade on a SOCOM 16.
I am a fan of them, although they do take some getting used to when getting out past 35 yards. I find the larger dot somewhat difficult in making accurate shots out past this distance.
They are wonderful for quick sight acquisition at shorter ranges. If I had any advice to give, it would be to go with the smaller front.
They are very well made sights.