Well, it turns out we were maybe a hair too optimistic.
As ever, let's remember that everything is relative. Expectations for S.H.I.E.L.D. are high and any time a show continues to have audience attrition over a long period of time, it's unwelcome news. Still, the Live+7 numbers (people watching on DVR and other time-delayed methods) are great on this show, and its overall ratings are better than anything ABC has had in this slot in nearly a decade.
The series is performing well by ABC's standards for the time slot and there is no reason to believe that it is in danger of failing to get a second season.
All of that said, this is a fairly significant step down for the series. It scored a 1.7 share in the demo, down from 2.2 for its last new episode (and the one before that). The last two episodes were both adjusted up somewhat after slightly-lower overnight numbers, but we're talking about a +0.1 adjustment, not 0.5. The odds of that kind of bump to make it even with its last new episode are very small.
Combine that with a much-hyped lead-in to the Sif/Lorelei event, a weeks-old cliffhanger involving the potential death of the show's second lead and a new Captain America: The Winter Soldier TV spot, and it seems as though Marvel pulled out some big guns and came up a bit short last night. If this fall's Thor: The Dark World tie-in are any indicator, we'll get a bump next week when Sif and Lorelei are actually featured, so the focus will then be on audience retention through the "Uprising" event they've teased, which will tie into Captain America: The Winter Soldier and usher in a new status quo for S.H.I.E.L.D. and the show.
Paxton plays John Garrett, a S.H.I.E.L.D. Agent from the comics who has a history with both Coulson and Ward. He'll be recurring for the rest of the season, and has a particular interest in the Deathlok program--which makes sense because in the comics, Garrett has a bit of android in him.
The impact of The Olympics and the related hiatus may have been particularly hard on Agents of S.H.I.E.L.D. After the previous break, the show returned a week later than most and didn't air as many new episodes before going on break as other primetime shows. Then it went on Olympic hiatus and came back a week later than many other shows. All of this may make it difficult for fans watching live to keep track of when there's a new episode, and may result in an even bigger Live +7 bump.