Transitional chapter. The first part is an obvious hope spot (the subordinates are bolstered by Hitsugaya's (too easy) defeat of Bazz-B, setting up their hopes being crushed further down the road) and, unfortunately, Soifon does turn up. I'm not surprised, I'm just not entirely thrilled, although it does bring with it some interesting information.
There are four interesting things in this chapter.
Interesting Observation 1: Reiatsu predicts blood kinship
Related individuals have types of reiatsu that overlap. BG9 seems to set the marker at 50%, but I'm more interested in the idea that reiatsu can be analysed to predict blood kinship. I wonder if this is setting us up for something as it has quite far reaching implications for a variety of characters that are indicated to have blood kinship throughout the story. It seems like a set up for something that'll occur or be revealed further down the road - either confirming blood kinships, revealing people aren't blood relatives or revealing people are blood relatives. I think we should file this information away and not forget about it.
Interesting Observation 2: Shunkou has forms and techniques
Shunkou has different variants, possibly determined by the nature of the person learning it. Soifon's is Wind. That does obviously beg the question of what Yoruichi's is (I don't want to go the obvious route and guess Earth given that her kidou lines were sinking into the earth but I'm fairly confident it won't be the same as Soifon's). There's also an acknowledgement of the role of resolve (yet again) in being able to achieve new levels of power: without the urgency generated by the loss of her bankai she wouldn't have felt the pressure required to push herself to the level she's reached. Soifon's comment 'Mukyuu Shunkou' - is that a technique, or is she simply confirming that her shunkou can function indefinitely throughout a fight as she claimed? Judging by the following page, it looks like a technique. If so, then not only is it implied that we have different forms of Shunkou but that these different forms also come with their own set of techniques.
In this sense we do see an advantage for Soifon not having used it in battle against the Espada: it's left the quincies with no intel on the completion of the form (ignoring the post-completion mastery she's gained since losing her bankai). So, we have a key indication that the quincy research does indeed have its limits, and that the quincies have not been able to find out everything there is to know about the shinigami.
So, at least we finally have some kind of sense of a difference between Soifon and BG9. Soifon boasts there isn't a time limit on how long she can use this power for (not the first time this has been important - she said the same thing to Yoruichi about her shikai). When dealing with the sense of 'robotic', fuel can be an issue (which is why, in sci-fi, there's sometimes the case where the big bad robot that can't be stopped suddenly runs out of power and shuts down). Of course, given that Uryuu introduced the idea of using reishi as 'quiver' for unlimited arrows (his Letzt Stil form versus Mayuri), Soifon's introduction of the concept of the 'non-stop' power does raise the issue of her opponent being a reishi-specialised creature (quincy) in a reishi world. This issue of 'non-stop' power may be relevant, not only for this, but because of what we've seen of BG9's gun, which looked like it was designed to keep firing lots of bullets (bullets or modified 'arrows'?) for a 'longer' period of time (longer than real life, I'm thinking).
So, we have the character who's designed to float like a butterfly and sting like a bee against... something very physical. But that does seem to be a transition for Soifon: the hornet uses the wind, now she becomes it. And she gets a chapter title that would make a good album name... oh, look, it already is: Deep Purple's album 'Stormbringer', containing the song 'Stormbringer' (the first verse of which is basically what's happened in this chapter).
Interesting Observation 3: The 60 Million Yen Man?
BG9. Yes, he comes across as a bit robotic. I'm inclined to head in the 'Bionic Man' direction, however. We know that sort of thing is likely to be possible given Mayuri's comments to Szayel about replacing parts of his body, and also given that Hinamori needed to have replacement organs grown for her by the 12th division. However, he seems capable of accurate detection through walls, given how he was able to go through the wall to hit Mareyo on the other side. His abilities seem a little... actually they remind me of something I can't quite place. I'll have to think about that. Anyway, his helmet has been hit twice, very hard, in this chapter and at the end of the chapter, it's cracked. Whether we get to see his face eventually, only time will tell.
Both BG9 and Soifon admit they have slightly inaccurate perceptions of the other. BG9 thought Soifon's shunkou was incomplete but wasn't correct. Soifon commented on quincies supposedly being archers (echoing the question Ichigo asked Kirge) but indicating she's pleased to be wrong. Is she wrong just because BG9 starts off by spearing things and whipping out a big gun? If it's one of the first weapons he wants to use, it's not going to be his best ability.
Interesting Observation 4: Haschwalth lied to Kyouraku
Last because it's possibly the most significant right now. Bazz-B implies the initial clash was nothing more than a test of the opponents (shades of Soifon versus Ggio, really). The idea that they'd spend time testing the opponent (which also indicates why BG9 was so interested in Soifon's shunkou) contradicts Haschwalth's implication to Kyouraku that they've gone straight in for the kill. It indicates the quincies are still intent on gathering information about the shinigami and are willing to spend time doing that rather than trying to kill from the outset. So Haschwalth has not been entirely honest with Kyouraku. There's still more going on here than it seems.