The complaints people have are largely ridiculous. The day 1 DLC is literally nothing but cosmetic things to make you stand out in Co-Op play. The Potato Sack was an interesting and unique marketing strategy, which people blew way out of proportion. As for game length, it took me easily twice as long as the original game to finish, and that was on Single Player alone. There is still an entire Co-Op campaign to play through, though I have read it's the shorter of the two.
When it comes down to it, Portal 2 is exactly what people should have expected. Anyone who expected anything different should go back and play the original game to remember what this series really is before they start BAWWing all over the internet.
Now, that done with, my experience with the game so far is amazing. It is exactly what I expected from a Portal sequel given a better budget. The dark humour is there in force, the voice acting is superb, the puzzles are extremely well crafted (and in general more complicated, but less twitchy than the original) and the game looks gorgeous. If you liked the original game at all, I would strongly suggest you pick this up: even with a single player campaign that lasted me about 6-7 hours, I felt I'd gotten my money's worth, without even touching Co-Op.
