Regardless, I felt somehow compelled to check out the opening episode of the new Shakugan no Shana S OVA. So what did I make of it? I'll answer that in just a second, but right now I've got the 1980s on the phone... Apparently they want their body swap concept back.

Yes, that's right, this first episode of Shakugan no Shana S sees Shana and Yuji inadvertently swapping bodies, after the latter discovers some kind of telescope with special powers as the pair hunt for something belonging to a Hunter. That's basically a summary of the entire episode's plot in a nutshell, so you can probably guess the rest - Shana gets annoyed at Yuji's subconscious moves to touch "his" chest, Yuji in Shana's body gets into embarassing situations such as walking in on a bunch of girls changing, and so on.
All in all, the entire thing is highly predictable, but to be fair the fact that it only lasts for a single episode keeps the idea just about fresh enough to make it fun without running into a dead end or overly abusing the potential for fan service. Perhaps more importantly, both Shana and Yuji's voice actors seem to have genuinely enjoyed the experience of voicing one another's personalities, and while neither party gets the others character quite right there was probably more amusement to be had out of Rie Kugimiya trying to play mild-mannered Yuji and Satoshi Hina trying to do "the tsundere thing" than the actual body of the episode itself.
I suppose if you're a big Shakugan no Shana fan, then this series is aimed at you from the start - I can't deny that there was some fun to be derived from this otherwise tired old scenario, but hopefully the remaining episodes of the OVA will have a little more meat to them.