I have used Aimpoint M68's on both my military issue and personal weapons. You can usually find them used for around $250, which is what I paid for my last two. I have never had an issue with any of them, except for dead batteries, which was my fault for not checking them.
I have used the Eo-Tech. I do not like it as it seems to be too "busy", as I like the single dot instead of the ring/dot of the Eo-Tech. That being said I think that a Eo-Tech would be nice for a shotgun with the 65 MOA ring, but that's just me. The AA model Eo-Tech I have never had a reliability problem with. The "N" models I would run away from. I have had to deal with four of them acting up where they would lose contact somehow with the battery and would no longer turn on.
As far as the primary arms red dots I have one of the small micro type models on a MP-5 clone that has been very accurate and reliable, more so than the weapon it is on.