Power, temperatures, and noise
This graph shows why we think Radeon HD 7750s should be passively cooled; the technology to use fan-less heatsinks on low-power GPUs already exists.
Temperatures are pretty good. We'd expect as much, really, given that HIS is using a dual-slot-taking heatsink.
Noise is kept to a minimum. Logs show the fan speed rises from 39 percent at idle to just 41 percent when stressed by gaming. This is one area where HIS excels.