I think screaming when you're expressing something angry or whatever is all well and good, but it gets old. If you have like one song an album that's just a big screamfest, that's all well and good, but making it so that indistinguishable lyrics that sound like they're being sung by a jungle cat are part of your style, it gets really old. It's like "Yeah, I get it. You're angry."
But then, that's just me. I guess if people are listening to it and enjoying it (and they enjoy it themselves), they're just as legitimate as every other musician/band.