I was very recently a sys admin at Brandeis University (sold my house and semi-retired!), and for my servers I used Black Box KVM switches. We had 3 16 port Affinity boxes linked together. They were pretty bombproof. All I can say about them is they did what we wanted and never complained. We had both PC's (win and Linux) and Sun boxes hooked up. And as we added more and more machines we just kept adding more KVM cards and boxes. Nicely expandable, and the built in software worked well. Good security, and fairly easily configurable.
Their KVM terminal extender is a nice option too. Outputs a video terminal up to a 1000 feet from the KVM switch, over basic network wiring (I had one in my office so I didnt have to get up every 2 minutes).
Based on my experience I give them a high recommend.
They are a little pricey though.