As a reader of the original novel (still in the process of watching the Anime & Donghua) I must start by saying there were parts of this film that I found pretty off-putting. For example, I was disgruntled that Liu Hao (such a key antagonist, IMO) was written out of the story. And don't even get me started on Chen Guo's character! I deducted a whole star just because of her. :( Don't get me wrong, the actress who played her was fine, but I hated the fact that her personality was made so weirdly clingy and airheaded. It was impossible to relate her to the original Chen Guo at all. I also thought the interior of Happy Internet Cafe was completely unrealistic (honestly, who could game properly with all that ambient light glaring off the screens?)
That being said, if I had watched this series before reading the novel, I probably would have loved it. Even with all my nit-picks, it was still great. The cast, script, CG and soundtrack were pretty darn near perfect. Even the added content was surprisingly solid. For example, the flashbacks with Muqiu, and those little philosophical object lessons Ye Xiu used to explain things to people. And I was grateful that the added/altered parts with Ye Xiu's family brought some much needed emotional depth and humanity to the story and Ye Xiu himself (the novel really didn't provide much character development for him as a person).
I will also say that I'm SO glad the writers didn't try to add any romance, and kept the interpersonal dynamics ambiguous, just like in the book. I really hope they'll make a season 2, because there's still tons of story left. I would absolutely watch it in an instant!