Just figured that I'd mention that this currently seems like the version of unity we will go with. I had been planning on at minimum doing unity 5.4 (Raptor was on 5.3.5p7, as 5.4 was still in beta at the time). But the advantages in 5.5 seem pretty nice thus far (some of the GPU instancing stuff, and the better line renderers and the better compiler), without a bunch of bugs that I can see thus far (5.4 was frequently pretty rough during the beta).
This talks about some of the benefits to the particle system in particular, which always makes me happy:
https://blogs.unity3d.com/2016/08/30/get-the-unity-5-5-beta-now/A lot of the core features that I'm excited about were already in unity 5.4, but the difference in performance is a noticeable thing between 5.3.5p7 and 5.5b3 for my current test project. I went from 500fps in one case (rendering a highly-detailed sun close up) to over 2000fps. This is on a GTX980M, vsync off (really vsync is like the worst thing ever, I hate it. Gsync or go home, heh -- I hope that becomes the standard, anyway).
Oh, and with MSAA on, since I'm using Forward mode (unlike Raptor I don't need a million lights and thus deferred shading). That oddly makes HDR impossible for some reason, which I'll have to look at, but I can still use Linear instead of Gamma, which is for the most part good enough for me for now at least.
This is the first version of Unity I've ever used in any sort of real-world context with the secondary-thread render batching processing, and holy smokes I am in love already. I am also amazed that finally they fixed the DX11 renderer for the editor itself; it was always fine in games for me, but on multiple computers and multiple sets of drivers the DX11 view of the editor itself was a bit bonkers for me. Strangely the DX9 view actually was super blurry on text in 5.5b3 for me, but hopefully that's just an editor thing, sigh.
At any rate, I'm quite pleased. DX11 equates mostly to OpenGL Core 4.1 IIRC, so this doesn't harm Mac or OSX compatibility -- just in case anyone was worried. I'll probably target builds at DX9 and equivalent unless I have a reason not to, anyway, though.
Today has been a lot less work on the design doc, and more stuff like this as well as a variety of interesting design discussions in the Ideas subforum here. I just needed a break from all those miles and miles of ship definitions, whew. And not having anything visual to show you yet has been stressing me out, so I wanted to get to that sooner than later, too.