I have the reaper in the ddr2-800 flavor. It works great, but I haven't really tried to push it (currently at 4-4-4-12 @ stock speeds)... nor do I intend to. The ram runs very cool... but I highly doubt the heat pipe is responsible for that (it probably helps a bit... but not anything huge). Honestly, the heat pipes can get in the way if you have a large cpu cooler.... adding an extra 3/4 of an inch to your ram just makes things clumsy in the case :/
That being said, after rebate and a combo deal from newegg, I paid $30 for 4 gb of pretty nice ddr2... I'm very happy with the OCZ and would buy it again. In reality, all the big names make pretty damn good products.... I tend to just buy whatever ram has the best price at the time (given a certain baseline performance that I am looking for). Mushkin has always been a pretty good brand. I wouldn't hesitate to buy from them again.