1 My first impression was that of purely American cartoon, so I wasn't enthusiastic. But leaving japanophilic prejustices aside, it seems like a vary solid non-stop action (I heard Black Lagoon was like that). The most annoying part for me comes from incessant continuity issues. I could survive Kamina's shades appear and disappear magically. But how about this: we make a badger hole to the face, see a small segment, with the rest embedded into rock. Next shot, access to the top of mecha is clear. And then, we just run through magically appearing tunnel sized for a train. It's like a better drawn Road Runner. OK, Yoko's boobs are pure magic, but otherwise this looks like a total loss. Even the saturated color key can't help.

2

Yoko's boobs are pure magic

Not to mention her butt.

Yeah, the continuity in episode one was pure flakiness.  I just assumed that it was discontinuous - that there was stuff going on we didn't get to see.   But even then, everything about the tunnels was nonsense, so at best its discontinuity plus poetic license.

Once they reached the surface, things got a little less random.

3 I understand the poetic license. For instance, Gurren wears eyeshades when Kamina pilots it. It's like Yurie's hair becoming long when she applies magic. But the continuity issues are sure annoying.