I have been riding Keos for four seasons, three different models, for thousands of miles. Never in those miles have they suddenly unclipped during a sprint, incessantly squeaked, caused joint problems, or required servicing. Such a trustworthy but rarely discussed crucial piece of equipment deserves a brief mention here.
Contrary to the picture below, I stick with Keo Max for track bike criteriums because it's a narrower option making ground clearance easier in tight corners. I'm sure the below mentioned models would also clear, but I like to stick with what works! In the years since the Keo Max debuted there have been more advanced Keo pedals produced, but my 2011 Keo Max set never fails, and I continue to train and race on them.
The Keo Blade model has a carbon fiber blade (offered in three different release tensions) rather than metal spring, that snaps the cleat into place. This model is wider (and lighter) than the Keo Max model, which makes it feel more secure and stable, although I can’t say it functions any different. Basically, the wide and stable platform feels solid!
The 2014 model, Keo Blade 2, has a much larger carbon fiber blade that is located below and in the center of the pedal—an engineering improvement that provides more surface area for the blade and protects it from pedal scrape. The latter is a considerable improvement for zealous criterium racers, as the portion of the pedal that is most likely to scrape the ground while pedaling through a corner is now not a functioning component of the pedal. If those weren't reasons enough, this model is aerodynamic and very light at 90 grams.