Simply put: These goggles are awesome! I've had many pairs of kaimans since I started 2 years ago. Everything about it is perfect for me - the fit, the suction, the comfort of the suction, the visibility, etc. I know some people don't like the kaiman, but I kinda swear by them.
Having a good pair of goggles is like having a proper bike fit - it really depends on a person's facial features as much as how a person's body fits any particular bike frame. There's a science to choosing the right type of goggles for triathlon or long-distance swimming and I shall delve in that topic very soon.
Meanwhile, based on my own facial features (asian, round, flat-nose), my personal best pair of goggles are the kaimans.
I've tried the clear lens (great for evening swims), and the black and mirrored lenses are great for swimming in the open sea espeically when your breathing side happens to face the sun! Don't get me wrong but the darker lenses can also be used when swimming in the evenings.
I usually get them from www.trisports.com although I've gotten 2 pairs (separately on 2 different occasions) from Amazon.com, and that's coz I got other non-tri stuff as well.