Does Anyone Know of a Good Quality USB KVM?

And now, dear readers, I ask a favor. I have a PC (for work) and a Mac (for life) in my home and they share the same keyboard, mouse and monitor. I have an old PS/2 KVM box that works really well so when I bought the Mac I wanted to hook it in to the KVM. The problem is that the Mac only uses USB peripherals. So I made the mistake of buying the Y-Mouse, an adapter that converts PS/2 connections into USB connections. As I explain here, the Y-Mouse does not work very well for me. So what I'd really like to do is buy a USB KVM. I actually don't care about the "M" (e.g. Monitor) part, I have a HP 2335 and use its built in monitor switch (which guarantees me the absolute best image possible). So what I really need is a USB Keyboard/Mouse switch.

I did some research and all I could find were complaints about USB KVMs, the main issue being switching time. It seems that switching between machines can take several seconds. Does anyone know of a good quality USB KVM that can switch really fast? If so please drop a comment on this article. Thanks!

N.B. I am aware of Synergy. But Synergy has never worked very well on Mac's and my PC is actually running a VPN which ends up meaning that the keyboard and mouse commands would have to be routed over the open Internet, this is both a security and a performance nightmare.