That thing is not an OC water rig. It's aimed right at running silent, and not much else. See, It's passive and not active. There isn't one fan on it anywhere. And, it's basically a large finned reservoir. No double pass copper tubed/finned/tanked radiator with a fan on it. Nothing to actively get rid of heat while OC'ing at all.
It does a lot to run a CPU silent, and runs at about 51C stressed. That's on par with a stock HS/F. So, to over clock with a Reserator is about the same as overclocking with a stock HS/F. Not going to get far. But for a normal PC, i guess it could be nice if you had that space. They sell for about $205 online, and that's also on par with a cheap active water cooling setup. But you know what? An active rig can also be ran at about 30dB total, so that's pretty quiet AND it'll OC further. Not to the hills, but it'll beat a normal HS/F.
Zalman put out a great idea though. It sparked a lot of minds into realizing that they don't need these whinning fans in their PC's just to run. Imagine your PC right there. Now, I don't know if it's loud, but I bet you can hear something. But imagine hitting the power button and all you hear is the HDD quietly ramping up. That's so fregg'n sweet! Once the drives are up, the silence is golden.
Innovatek also has a tower. While it's about $100 more (last I checked), it's a mory sexy disign IMO. The Innovatek rig looks more powerful...like the HongKong skyline. The Zalman...well...it's phalic