I think it is as good as most high end piano, drums and strings samplers.
If you take a real string section and compare it with a sampler, the difference is huge, but when you put it on a mix it doesn´t matter that much. They both fulfill their role on the song and can bring the same emotions to the listener. You know, just like when you use a bass sampler instead of a real bass. The real bass has many nuances and playing techniques, but if all you want is a damn low end on your mix, a sampler can do the job just fine. IMO guitar samplers can make the role of the kickass bang-your-head riffage element just fine. I think they should even simplify these libraries for the task like Shreddage did.
That said, I think Electri6ity is too expensive. If you think you can grab Native Instruments Komplete for 500 bucks...