Wow, I expected it to run nowhere nearly as smooth as it does for me. It's actually pretty okay, yeah, frametimes aren't as consistent as I'd like them to be, they're not
good but they're not terrible, the overall image is really quite smooth.
I have only had a quick go of it so far, driving the batmobile around, flying around, etc, but I can see myself playing this through and not being all that distracted by the performance. My FPS range was no lower than 65fps and average somewhere between 75 - 85fps with no big dips.
I'm playing it at 2560x1440 on:
i7 4770K @ 4.6Ghz
16GB RAM
GTX 980Ti
Game on an HDD (I had it on an SSD when it first came out)
G-Sync
All NVIDIA settings off with all other settings max.
I'm fairly happy, not overall, of course this game could and should have been so much better on PC, but I can see myself playing and enjoying it in this state.. providing my 5 or so minutes of gameplay wasn't representative and I run into some real problems in some particular areas - what I tested is what gave me a lot of problems at launch (batmobile, general navigation outside of the batmobile and fighting) and that was all fine.
Benchmark results for whatever it matters (I don't think it's all that representative):
http://i.imgur.com/DW8qItg.jpg - of course ignoring the minimum, that 13fps is from when the benchmark hasn't really loaded.