The OCZ EvoStream 600W leaves me with mixed impressions. Yes, the unit has awesome power stability, better than any other PSU we tested so far. But on the other hand the lack of proper fan control makes this unit one of the loudest, too. The modular concept works very well and allows you to reduce the cable mess in your case.
If you care about energy efficiency this may not be the best power supply for you, but the differences are quite small anyway. In my opinion the EvoStream is the right power supply to get if you are a hardcore overclocker and want great voltage stability and noise is not so much of a concern to you. If it is, you may be better off with the quieter OCZ GameXStream, that comes at a similar price and offers very stable voltages as well.