It's amazing how many people have forgotten that Valve doesn't just churn out sequels (L4D2 even had significant improvements, and very few people who liked the first hated the second). Portal 2 will be one of the best games ever created. There is no reason to assume differently. The core experience is true to the first, what with the humor and devious puzzles, as well as the atmosphere created by GLaDOS, while there will be massive improvements, such as variety of location, longer storyline, an additional standalone co op storyline involving even harder puzzles, and an overall more polished experience, given how huge the development team is this time. Don't go crying over how Valve will ruin Portal just yet. I for one will be at the front of the line ready to have a slice of that delicious pie. (thought I was gonna say, cake, didn't you?)