The biggest issue I can see with this power supply is that almost nobody will need a 1200W PSU. In our testing we saw good voltage stability and very high efficiency rating, which makes this PSU a great choice if you are looking to power a super-high-end system.
The bigger form factor should be no problem for power users who either have a full tower case or use an open bench for testing. Sunbeam has done a great job with the package, they even include some adapter cables. Especially the PCI-E extension cables are very useful because they give you even more room to work with your video cards.
For such a versatile PSU it would have been a great additional feature if some of the cables were modular, so they could be detached when they are not required. This would help keep the case insides clean of any unwanted cable mess.
Still, if you need a PSU that can pack a punch you should definitely take a look at the Sunbeam Tuniq Ensemble 1200W.