I purcahsed the Unablock from them a few months ago.. Aside from it comming with a few missing washer or something, I have been happy.
I lapped it up a bit, and then hooked it up.
Personally the plexi-mount makes me nervous, and as no bolts are running through the block itself - good luck getting it to stay still if you ever need to remount it with water in the lines.
Anyhow.. if you have a low flow system, I'd reccomend the Unablock. I use it with an '89 camaro heater core and a Rio180 pump.
Running my Xp1500+ @ 1.5 ghz 1.84 volts, keeps it at an acceptable 43C or so full load. Though I'm sure that will rise in the summer. I'd still reccomend the Unablock over a plain block.