Civ 5 was finally available in Europe yesterday on Steam. In spite of being a Civ veteran, I first did the 5 small tutorial missions (the third one is tricky until you realize you need to build a palace in Rome), and the 1 player against 1 AI tutorial game. Now I'm on my first "real" game, with 6 players and 12 city states.
Up to now everything is running fine, and you quickly get sucked into the old "one more turn" flow. The new combat system takes getting used to, but is superior to the old system in my opinion. I also like the new hex-grid much better than the old square grids. I very much appreciate the mix of "this is still Civilization" and the various changes and new features.
Sometimes the game seems to slow down a bit, even on my relatively powerful PC. And I'm somewhat annoyed that the game setup menu doesn't appear to save settings, so every time you start a game you need to manually set all your favorite settings again. But apart from that I'm quite happy with the game. Recommended!