The harsh vocals have a lot to do with establishing balance between the pop (or, rock) and metal in that record, which was done superbly. On the surface level, I am accustomed to bands alternating between cleans and growls in modern metal, and I am used to that effect, but whenever I listen to Static Impulse, I am reminded of how it exactly works and why is it so overdone as a formula (answer: because it's successful).
Modern melodeath/Gothenburg metal is quite similar to pop in terms of structures, catchiness and repetitiveness, both within the genre itself and within one album because the formula is so precisely defined. The riffs (mind you, I'm talking about the modern variant of the genre here) are often more melodic than in most other genres of metal, and when the (relative) lightness of it all is put against harsh vocals, you get an interesting product, which is why there is a ridiculous overload of bands in the genre - people just find that interesting and it's easy to emulate.
Static Impulse goes one step beyond most of those modern bands - the drumming tends to be more aggressive than usual, the harsh vocals are slightly more varied, there's shredding both on the guitar and on keyboards, but those aggressive elements are not only downplayed by the "regular" pop sensibility of modern metal, but also by the extreeeeemely catchy choruses (I rarely hear something as catchy as Mislead or One More Time), by Matt bringing some more modern overtones on keys, by having very simple, non-evil or anything like that, down-to-earth lyrics growled, which is quite fresh and interesting, and by putting straight up pop songs (Euphoric) on the record. Now that is one interesting playground for James, and I think it becomes him perfectly.
I mean, I'm not saying it's a really original album, both in general and in the genre, but it just goes one step beyond what you can normally hear in modern metal when it comes to maintaining that fine balance - the edge of the blade is sharper, and of course, it helps having such interesting players and one of the best voices around to make it really work.