Episode 20 pretty much sucked (WTF?! Floating brains?!). Well, it wasn’t that bad, but did we really need another setting the stage episode? Vivo’s a battery, the TSAB is in shambles, Ginga’s a mech, and limiters have been released. Let’s take on the final boss already. Regardless though, we see Nanoha’s barrier jacket while in Exceed Mode in action. It’s in the ED (and the OP?), but now it’s out and about now.
As for the barrier jacket, I like it a lot more than her usual 19-year-old Nanoha barrier jacket. Exceed Mode (Excelion Mode’s new name apparently) is quite reminiscent of her A’s barrier jacket with a bit of Hayate’s look. The long skirt is back, which I welcome, and the top jacket is open. Plus, the ribbon is gone, giving it a more mature look. Definitely looks more upgraded, but familiar. Also, the black on her upper chest and neck look pretty slick. The heels though, I could do without. They work with Fate, but not with Nanoha I think.
Interestingly enough, it was revealed that Fate has another mode up her sleeve as well. Sonic Form from A’s was pretty cool, but it was akin to her barrier jacket from then. I’m really wondering what her barrier jacket for that looks like (if it changes at all). Perhaps Fate has a third mode as well… but that’s probably just wishful thinking on my part. As for Hayate, she’s neglected as always. 
At least she’s in action in episode 20, so here’s hoping she puts her SS rank to some use.
After ep 19, I was hoping 20 would be a fighting episode but we get {like you said} ‘another setting the stage’ episode. But hey, 21 looks like it will have the fighting…and Subary+Ginga encounter!! {Really excited about that one ^_^}
As for the jacket…somehow those heels doesn’t fit Nanoha {but the design is good}. Everyone is used to her shoes and changing it like that just looks odd. And that black chest plate looks awesome, wonder how she’ll look without her white corset though.