I've had the dual-tuner version for a few months, and I love it. I have two Windows 7 machines (one wired, one wireless) with WMC pulling HD channels off of a single unit simultaneously, with no lag or freezing.
The dual-tuner model, for those asking, turns any ClearQAM channels on your cable system into accessible data streams on your home network. That means that you can view these channels on any computer on your network by using either the included HDHomeRun software, Windows Media Center, or other compatible third-party software. No additional hardware is needed!
ClearQAM channels are the ones that are unencrypted by your cable provider. You can check to see which channels are in the clear by attaching your cable directly to your HDTV (bypassing the cable box entirely), scanning, and seeing what you come up with. For instance, I get all broadcast networks and a handful of international news channels.
I don't own the triple tuner model, but since it has a CableCard slot, I imagine it's capable of tuning all channels, ClearQAM and encrypted alike. Call your cable company to make sure they offer CableCards!
Also, a quick note about the number of tuners. Each tuner allows a single data stream at a time. So, with two tuners, you can have two computers watching two different channels, or one computer watching one channel and recording another channel. The three tuner model can either stream to three computers, two computers with one recording, one computer recording two shows and showing one, etc etc etc.
EDIT: I should add that the device itself isn't wireless. Once you connect the tuner to your router, any device that connects to that router can access the tuners. Even on WiFi.