They work just fine in my experience.
I bought one of the CP Tactical Red-dots at Walmart for $30 and zero'd it on my 10/22.
I have mounted it on my 5.56AR15, 300Blackout AR15 (7.62x35), and AK47 Pistol and it still holds zero. As a cheap RDS I'm very satisfied with it.
For reference my AK47 pistol (Draco 7.62x39) has a very powerful recoil and the RDS has not lost its zero.