Johnnyguru is one of the most well known and PSU reviewers. Companys just send him tons of them in hopes he will review it and give it good marks.
Johnnyguru's Rosewill Reviews
Rosewill Xtreme Series Power Supplies Review
Rosewill RP500-2 500W Review
If you read the reviews in full you will see that Rosewill PSU's have EXTREMELY stable rails. The RP500 actually was underrated and could perform at above the ATX voltage specs at it's rated watts.
The other 2 power supplies had very good rails as well, the 840W was acceptable at 11.84v on the 12's at 100% load. Where as the 750x had 11.94v, meaning it was perfectly stable.
If you look at a reviews here on the 500w modstream
Overclock3D.Net :: Review :: OCZ ModXstream Pro 500w :: Text Config, Voltages, Effiency & Temperatures
bit-tech.net | Review - OCZ ModXStream Pro 500W PSU
When weighting the 12V rails (which is what gaming and most desktop computing will do) just as the JG Rosewill reviews were, the 12V at max load is 11.85-11.9v which is still very good. However, it's as good as the worst performing rosewill that was reviewed by johnnyguru; with the 750w putting out 11.94V and the 500w giving out a 12.14v, showing it's actually underated.
Rosewill PSU's are extremely stable, and they have no worse quality than low end OCZ PSU's. A few of main scares about Rosewill PSU's were that they contained no PFC, and that they died because of low ventilated cases. The new Rosewill such as the 530W I linked now contains PFC, and uses better caps for less ventilated cases.
I'm not knocking on the OCZ honestly, I mean 36A of stable 12V rail power on a modular PSU for that cheap? Really sweet if you need or want modular. However I'm just saying don't knock on a product until you look at hard evidence.