I also use the Mirrycle. I have it mounted down and in. That way I don't have issues with tight gates at trail heads and doorways. It also has helped when the bike fell on that side, mirror survived. Looks better too. If you have narrow bars or wider rider, the rear view could be blocked, if mounted down and in. Works good and I've never had any vibration issues.
Pro: price, adjustability, real glass with no distortion, works with most size bars.
Con: cheap looking plastic, glass can break (hasn't in 4 years).
Get 'em while they're hot! I noticed price has doubled in 4 years. Of all the bike mounted mirrors I see, easily 9 of 10 are Mirrycle.