I never got to play the original AH version of the board game (I wanted to but all my money went to 40K), but I do have the latest version of the board game and expansion from Fantasy Flight Games. It's pretty cool but the learning curve is steep and setup takes a while, so I've only gotten to play once.
As for Civ 5 expansion, I've played several games. Just duel maps with 4-6 players set at Prince. Seems like the AI doesn't attack as randomly as they have in the past and I'm enjoying the extra units that fill in the previous era gaps, like triplanes. Culture victory is harder now, but not impossible. I also was once penalized for having too large of an army. Not sure if that's new, but first time I've seen it. City states, which are one of the best things with V, are even better now. Religion is cool, but a little underwhelming. Spys seem simple at first look, but I can see some interesting strategies being used there.
If you only play Civ 5 only on occasion, probably best to wait for a sale on the expansion. I've been a fan since Civ 1 on MS-DOS and bought my first copy of Win 3 just because my DOS version of Civ was lost in a move and the only thing I could find was a Windows version of Civ, so the expansion was a must have for me.
Paul