I just managed to get a nightly version running (yay!) and in basescape/geograph it's just awesome. The added options are amazing.
I don't know what changed in the battlescape, but once I get there the game is super sluggish. My computer is crappy (Intel Atom dual core 1.6 Ghz, 1GB Ram, no graphics card, it's a tiny Acer Aspire One) but it ran 1.0 flawlessly. That's actually one of the reason I found OpenXCom: I was looking for old games I could run on a crappy computer.
In 1.0, if I try to use any graphic filter, performance becomes terrible, but that's fine I just did not use any. But in the nightly (1.0gcdf4ff1 ?), it's slow with no filter (I actually have not tried filters, since it would probably just get stuck).
For now, I do battles in 1.0, everything else in the nightly. But that's hardly a working solution..