What I don't like about the changes is that they force you to adopt a very military-focused strategy early on if you want to survive. I always like to start peacefully and get a couple of wonders built in my capital but it doesn't seem possible to play that way any more.
This is not what I experienced. I finished a Large Standard Emperor game last night (diplo victory) and I played peacefully next to China and Japan! I built the most wonders also, at least early game (Oracle, Pyramids, Great Library, Great Mosque, etc).
I did notice that the AIs expand more aggressively now, it even seemed like I was back in Civ4 with all those tiny cities spread all over the place. The AIs also backstab more, so you feel more afraid now than before, which is great.
So, overall I think there's more challenge now. The AIs are less reliable (but in an acceptable way) and you need to be even more careful and cunning with who you make friends with. You need to bribe AIs to attack others and really need to watch out who likes who and who doesn't.
In summary, I feel the game is better after the fall patch. The performance increase is notable. Before I couldn't play large games and they are very playable now. The renderer is also improved, it's much more smoother to move around. The AIs attack and move now, something I never saw before. The AIs also attack you on every chance they get, while before sometimes they just missed opportunities. They are more deadly (really go for wounded and critical units) and guard their cities better.
My only grip with the game still is with naval invasions and sneak attacks (or lack thereof). I didn't get enough sneak attacks and I failed to see naval invasions. Alexander and Pacal had more troops, more research and more everything and they hated me and they never attacked me overseas. I didn't bother with building garrisons and sent all my men to a front far away from my costal cities because I felt that they wouldn't come to get me. They could have just steamrolled me.
Something needs to be done about naval invasions and sneak attacks to raise fear and tension, two critical aspects in Civilization games in my opinion. After they fix that I think Civ5: G&K will be on an equal foot or even better game than Civ4:BTS. Maybe on a next massive patch or expansion.