Decided to pick up Star Cat again after seeing you'd mentioned it. The first episode gave me a bit of a Red Dwarf vibe, with Seitarou's slovenly life in space, his snarky robot companion and the computer's human avatar, so I was a little disappointed it got somewhat fluffier thereafter, but it was still fun. It's definitely a great looking OVA, I loved all the attention to small world-building details like the characters hooking their lifelines on to the ship during spacewalk or the jewel-encrusted maid robots near the end.
One thing that did strike me though was that, despite me usually having a tin-ear for VA performances, it seemed noticeable that the girls were played by non-professionals; their delivery seemed that little bit different to the other characters. Presumably much of the funding for the OVA was tied to promoting their performance as LISP, which I suppose says a lot about how much cash must have been flying around at the time - surely it'd only be at the height of the boom years that you could produce a such well animated four episode show just as promotional material for an idol group. Although I suppose AKB0048 is a thing...
Dokushin Apartment sounds a bit skeezy for me, but I'll be sure to check it out anyway, even just for curiosity's sake.