Well, my problem is more with the handling than the plot itself as you probably guessed, so the problem isn't that the plot itself is slow-paced, but that it's handled in a way that's boring (One of my favorite anime is actually .Hack//SIGN so you can probably figure how much I care about pacing, heh). I never got past that whole feeling that I'm watching a show, I rarely felt any fear myself outside of a few select scenes that I pointed out. I can think of a few things that could've made it more effective (Like, say, not showing any Grados at all, and have Eiji wear an opaque mask for a good length of the show, possibly don't show him in person at all, have him communicate to the civilians through code or something).
And yeah, I'm definitely past where you watched. I went and watched a bunch of episodes at once and I'm up to 28 now. I feel the show gets a lot better towards the end of the first season and I really, really like what they're doing with the second season so far.