Mushkin's HP580-AP has a highly polished metallic look to it. The color could be described as anthracite - it is not pitch black.
One side of the PSU has a Mushkin logo embossed in the PSU metal. I find such little details add to the overall professional look of a power supply and do not cost much.
The back has the modularity feature. As you can see the mainboard power cable and the 4 Pin CPU cables are fixed to the PSU, it would make any sense to remove them anyway. While this may not look as "clean" first it makes sense because there will always be small losses when electricity passes across the connection.
The highly reflective, glossy paint job means that fingerprints will stay on the case, but they can be easily wiped away with your hand or a dry cloth.
One very interesting cable is this ground connector. You have to screw it to your case metal by using any screw that goes into the case. This is completely useless because the PSU is already grounded by its own screws and by the various ground connections going away in the cables. According to Mushkin "this unit features a heavy-gauge ground/return wire to further reduce noise and ripple".
For the ATX power 20+4 pin connector my favourite method is used. The additional four pin connector can be locked into the 20 pin connector forming a solid connector that is very easy to use. Other clip-on systems can often be a pain to work with because the connectors do not stay together when you try to plug them info the motherboard.
The same locking princible is applied to the 12V power connectors.
This small LED on the back of the power supply indicates "Rail Fusion" status. When a single device exceeds the 20A limit per 12V rail, this features draws in additional power from the other rails to avoid an overcurrent shutdown of the PSU.