I just finished ep. 19, and so far it's been really good, some more Revy and Rock development, though I must say hearing the Japanese seiyuu speaking so much English sounded... odd. Sometimes I couldn't understand them, but Revy actually sounded pretty funny when she started going off in English. The actors definitely didn't have much practice with the language (Balalaika's actress I think had the most experience, while Rock's had very little, and Revy was moderate, sounded like some of the foreign students I taught at Uni).
I'm feeling more "hooked" from ep. 13 and on, there has been more character interaction, and possibly more action, which is odd since the one tends to outweigh the other.
Edit: I have now finished the series, and I must elevate my rating before to an 8.5/10, maybe closing in on 9 - there was a lot more development, more brush strokes that let us into the character's minds. Particularly in respect to Balalaika and Revy + Rock, plus Gin just kicked so much ass. I would now definitely buy the series, especially to see the English dub, I'm curious to see if they pulled it off well. From what I've heard it's a good dub. I'll be waiting for season 3, if it ever comes out.