Well, I just finished the PSP visual novel Sora no Woto: Otome no Gojuusou yesterday.
And it was really not as bad as I originally expected. While the game is indeed rich on fanservice and light on plot, it had that Sora no Woto soul in it and the ending was really, really sweet, tying up the strings of fate seen in the show ever so closer. Though you're starting to wonder, just how much did Iliya know in advance...
Despite the game being fanservice-oriented, the characters were portrayed in a pretty genuine way and the voice acting was superb, so there's that, too - the game had clearly some effort put in it depsite being the last Sora no Woto production to ever see the light of day and ultimately being resigned to remaining a fairly unknown part of the franchise even before it was released.
It's definitely only suitable for those who've seen and liked the anime series, since it doesn't work on its own whatsoever, but if you eagerly desire more wotos in your life, you'll probably enjoy it as I did. Essentially, this is a sweet moege fandisc to the series.
Sadly, the setting has not been explored any further - the authors probably thought that the game should not bring in anything that could potentially come in conflict with further productions. But there is no hope for another season or even an OVA at this point, so that was ultimately pointless and a bit disappointing. That said, there are a few drops of fuel for speculah here and there.
It's only available in Japanese for now, but the fan translation project is already at day 9 out of 12, though it will probably also require some editing work before it can be released, from what I've seen.
Aijou Yuujou, fellow wotos, and may the spider tanks protect you from giant apocalyptic birds.