Ditto for what sttubs said. For a serious overclocking project I'd spend more. But the CoolerMaster Hyper 212 EVO (. . .whatever) is a stand-up little cooler, which does a darn good job for $30.
Could be it's even cheaper now.
What to "watch out for?" That drives me to my overclocking enthusiast extreme. I don't care how it looks; I only care if it fits the case. It has to have a solid construction for mounting, but even the worst coolers using the Intel push-pin design are still OK.
What do I look out for? Comparison reviews and verification across comparison reviews. Whether it's an OC load temperature result across several different coolers on the same platform, or somebody's calorimeter measurement of thermal resistance, I always try to pick the cooler that has the lowest thermal resistance or gives a good showing even compared with AiO coolers. These days, you'll not likely find a heatpipe cooler that can outperform an AiO, but high marks are high marks.