Something I've really enjoyed about Secret Avengers is the feeling that it's an episodic TV show; each issue is contained within itself, and contributes to the larger story. This is great, because it allows for cast members to shift in and out without any weirdness - the team is "secret" after all.
David Aja's art is gorgeous, and thankfully he got to play to his strength here: kung fu. Having Shang-Chi as a "guest star" definitely makes me smile, and Aja's art style from Immortal Iron Fist contributes wonderfully to the fight sequences. Aja's faces have also become less gritty - this isn't a complaint, but I think it fits better with the mood of the book. It's very light-hearted - almost like Chris Samnee drew Thor: The Mighty Avenger - but still allows for some dark-ish moments.
Also going with the episodic TV vibe is Beast as the team's "science guy." The sequence at the beginning where he explains the multiverse and the consequences of what the team is about to undertake was brilliant. If there's one thing Ellis knows how to do, it's dry wit, and Beast is one of those characters that needs to be funny, but not goofy.
I don't really have a lot of bad things to say about this issue, to be honest. It's solid from start to finish, and gives you a good smattering of everything both creators have to offer.
Warren Ellis and David Aja are two of my favourite creators, and I can't imagine a better combination to pull of Secret Avengers. There is so much here that allows both gentlemen to work to their strengths: Ellis' technobabble-y dialog and Aja's beautiful kung-fu sequences both shine.
I'm not sure how much longer they're going to be working together, however - Ellis' run is rumoured to end soon, and whoever takes over from him will have some pretty big shoes to fill. However, for now, this issue can be remembered as one that stands on its own two feet phenomenally while still tying into the over-arching story. Give this one a buy.