I have Burris FastFire 3, Leupold Deltapoint Pro, various cheap clones and latest addition is the Nikon P-Tactical Spur. The Leupold was my favorite but the new Nikon may take that position. Things I like about the Nikon:

Reasonable cost at about $220 shipped (about $130 less than the Leupold)
Remembers the last selected intensity after power down and back up
Battery replaced from top so do not need to remove sight
10 intensity levels
Clear glass
Seperate +/- intensity buttons on the side

Nikon:


FastFire 3:


Leupold:


$50 Clone: