You start the game in 1500, Ezio is 40ish. Not sure of the timeframe, haven't beat the game yet.
If you're new and Brotherhood is your first AC game, you get a nice little recap intro video of Desmond's story when you start story mode.
I wasn't totally praising the Full Sych thing, it's annoying in Romulan Lairs where I have to complete it within 8 minutes. I absolutely hate time limits outside of racing games. It's also annoying when I have to go undetected as my LS stick is fucked. If I don't ease the stick into neutral, Ezio will jump out of whatever haybail he's in. But that's more of a personal issue than a game issue.
The coolest thing I've seen yet is in a mission when I was required to call in some recuited assassins to kill a guy. I was chasing him down the street, he turned a corner and...
BAM!
one of them fell from the sky and air assassinated him. Now I know how I look when I air assassinate people. Freaking awesome.