Saw mention of this while digging through your blog and I found reading this incredibly interesting. I love the use of HP as a universal resource that gets taxed for moving in darkness, being surprised, or failing group rolls; also it makes a great way to consistently represent getting lost in darkness in the dungeon or ending the session in the wilderness.(Although if I ran it I might even change the name of HP to help reflect that—maybe "vigor" or "energy". In one of your blog posts I think you mentioned possibly calling them "Heart Points" but the issue is when I see HP it still makes me think of physical injury regardless of what it actually stands for.)
Also unless I'm missing something, wizards are only restricted by how many spells they can memorize, not the level of spell; Wizard spell slots are "level-less" spell slots; I love that kind of vancian magic flavor. It keeps low level wizards from using world-ending spells, but it ensures high level wizards still have to think very carefully about what spells they prepare (Personally, I love OSE but MU's get far too many spell slots at higher levels). Plus the rules around spellbooks and how many spells they can contain! Priestly and Psionic "magic" also look incredibly interesting, though I think I need to read them over again to really comprehend what I read.
Even if I never end up scrounging the time and people together to run this for a consistent campaign (as it seems like it needs to really shine), this gives me a lot of good ideas to chew on. Excited to check out COBOLD #1 for the space-faring sphere-clipping rules!