Finally beat the game at around 22 hours. Did a few side missions on the way. Now at around 78% complete.
The lack of SLI support really dampened this game for me. Playing @ 5K w/ GameWorks gives me around 25 - 30FPS w/ a single Titan X SC. 4K is not bad (45 - 60FPS).
They need to fix this game - glad I got it for free!
Will wait for the full GOTY edition with ALL DLC, skins, etc. added to get the ultimate 'Arkham Knight' experience.