That didn't take very long at all, actually. I hit 50K late last night in Assassin's Creed 2, after finishing a particularly flashy bit of killing.
AC2, by the way, is amazing. My initial concerns were probably just me trying to keep my expectations in check; I'm now at least 5-6 hours in and I'm totally in love all over again. In fact, I think the only reason why I'm awake so early on a Sunday (especially since I was playing until around 1:30 in the morning) is because I'm so anxious to jump back in.
My only real complaint is that sometimes the controls get fucked up. For the most part, the game tries to keep thing as simple as possible and so it'll more or less guess what you're trying to do and just let you do it without a series of convoluted button presses, but sometimes it guesses wrong and sends you careening backwards off a ledge instead of up the side of a wall.
OK - Venice, here I come!