1) Tons of minor graphic enhancements - polishing mainly...
1.a) ...includes enabling antialiasing on most lines (disableable by config), which greatly enhances the visuals on low-res modes.
2) First step towards an .ani overhaul, featuring multilayer animations - with full support for multitexturing. Right now: frame interpolation, per-frame texture coordinate range override (sprites only, for now), interpolation of texture coordinates (allowing efficient zoom/pan animation).
3) Animation-based gauges, where the value is mapped into the animation time
4) Tons of optimizations, in...
4.a) CSV parsing - also, besides faster, it's more flexible now, allowing usage of Excell
4.b) Savefile string save/retrieval
4.c) Python iteration algoritms
4.d) Mesh loading (less reallocations, less overhead)
4.e) Dynamic physics priorities (now they're back to low priority, but it detects when you're about to collide with a low-priority unit, and boosts its priority for the collision)
4.f) Drawing queue. Separated sequences into different queues, which improves drawqueue processing by around 60% (got from 15fps to 25fps on Penders Star - PR because of this)
4.g) There's a flag to disable damage sparkles - both incorrect and very inefficient for asteroid fields.
Perhaps there's more... but I can't remember. Enjoy.