Actually, that is a decent unit. I had thought that InWin unit was built by CWT, but it was made by Powerman. CWT makes mediocre PSU's *at best*
However, there are so many things that determine whether a PSU is good or not. Here are few, but I suggest reading a few PSU reviews at jonnyguru to get a better idea
1. Ripple suppression: Actuall current delivered varies widely many times per second, and the PSU needs to minimze it, sending as close to a constant to the res of the PC as possible. The worse a PSU is at this, the shorter a lifespan other components have.
2. performance under load, under heat, and from cold start: some units crap out on efficiency when pushed to near their max load. Some units can't even reach the advertised max load at all without dying (some PSU vendors are sleazy and will list the unit according to it's peak voltage rather than it's RMS, thus you could see a 350w PSU from one manufacturer able to actually push more wattage than a "450w" unit from another.) Some units have awful heat dissipation and will drop power instead of overheating, etc.
3. Construction: types of capacitors used, type and number of phases in the voltage regulator, heat dispersion design, soldering, etc. All this translates into how hard the PSU itself has to work to deliver the voltage and in turn, how reliable it is.
4. protection technologies on the PSU (or lacking protections) such as over-current protection (OCP) , over-power protection (OPP), under-voltage protection (UVP), active/passive power factor correction (PFC).
Hope this helps. Cheers!