I'm very tempted by the H70, and I'm planning to put one in my system when I get around to doing a CPU/mobo/ram/case/PSU upgrade. Probably next month. Water cooling "without the hassle" is a very attractive proposition. The supplied fans put me off a little though - reviews suggest that they are fairly loud, and have a somewhat high-pitched whine. But, if they are annoying, it looks easy enough to replace the fans with something a little more high-end like a pair of vipers.
As for the intake / outflow question... From a thermodynamics point of view it depends on the airflow within your case. In a sufficiently well ventilated case, it will always be better to drag cool air in - right over the radiator. However, with insufficient ventilation the increase in ambient temperature inside the case will cause a bigger rise in CPU temps.
Consider two temperature differentials:
- delta1 is the difference in temperature between the air just outside your case, and the air just inside, with the fan blowing out.
- delta2 is the same temperature difference, but with the fan blowing in.
Clearly delta2 is always going to be bigger than delta1 (since you're dumping extra heat into the case). The crossover in efficiency comes when delta2 = 2*delta1. So, if delta2 is less than twice delta1, then you're better off dragging cool air in. Given the amount of other stuff that burns away in a computer case, I imagine that most people will find delta2 < 2*delta1, and therefore want the air to be dragged in. Which is just what corsair recommend

Of course, by dragging more hot air in you will also increase the temperature of your GPU and other components somewhat, so it's not quite this black and white...
Personally, I'm planning on having the thing push air out. Why? Because the case I'm going to get (HAF-X) does not have dust-filters on the back, and I have a long-haired cat who sheds like crazy

But, in a dust-free world, I would do it the other way round.