I played my first game on Beginner, and it took over 12 hours. I suppose I could have cut half that time off if I didn't try to culture-flip the last two races. That failed miserably, btw. I think culture flipping is mostly useless this time around. I had every planet in the galaxy aside from 4, and every star port pumping out constructors that I used to make influence bases everywhere, I had a favorable-to-me influence thing going on in the UP, and I managed to get one of the enemy planets up to 6x influence. The best I managed to do was get that one planet up to 76% rebellion before my UP resolution ended and everything came crashing down, they all went back to 1.5-2.5x, and rebellion dropped to 0.
In fact, the only time I flipped anything with culture was the benevolent ideology path's "flip everything in your influence range" thing. I managed to take all 3 minor races, 2 Thalian planets, all of the precursor artifacts, and dozens of star bases in one whack with that.
I could have also made it shorter by just wiping out the last two races. My military was about 70x stronger than theirs, so it would have been easy. I had been trying to only attack people who had declared war on other, weaker races though. None of the battles I was in were even remotely fair to the other guy.
I guess the lack of reasonable culture flipping means I'm going to have to play far more aggressively if I want to win anything but an influence or research victory.
(I ended up just taking the easy research victory. it only took 6 turns past the time that I was allowed to research those last 3 technologies.)
Also, I played my favorite race from GC2, the Iconians. I'm going to probably try each race in this though.