The movie worked better for me on DVD than in the theater. After watching it on the big screen I just felt like something was missing. Here are my nitpicks:
1) The crew looked old. There was very little of the energy from the first three films in the actor's performances.
2) The reaction to Data's death was underwhelming. I also thought Geordi should've given Data's eulogy, not Riker. It just showed how little character moments, or understanding of the character's was evident in the film. (I will say that the reaction shots worked better on DVD. I got to see Troi and Geordi's subtle pain more. And Riker as well. But it was still too understated.)
3) The ending with Picard walking fast and smiling instead of the Enterprise trekking off didn't sit well with me. I liked the deleted ending better, even with Madden. It showed more of the moving on aspect which was one of the better parts of the film.
4) Troi's mindrape. How many times has Troi been mentally violated? I think the Trek writers have a thing for that-and even did it to T'Pol on ENT. If I'm not mistaken Seven got the business on VOY too. It just seemed warmed over and didn't do anything to establish Shinzon as a bad guy. We already knew that. It only served to give Riker and Troi 'cool' payback scenes.
5) Lack of character moments for everyone except Data & Picard. I really wished we could've had a little more interaction from the rest of the crew, and an explanation about why Worf was back, and why Wesley was back in uniform would've been nice too. Also, why couldn't Wesley be back at the Helm for the final voyage? It was a waste of characters, esp. compared to how the TOS was utilized in their farewell film. It's the characters that were at the heart of the TNG franchise, that's why I kept coming back week after week. I don't get this feeling that delving into their histories or referencing past events and using them to progress the characters alienates new audiences. I think audiences are pretty quick to pick up on things and if they have questions, there are a ton of materials-the TV shows themselves, novels, reference books, online resources, etc. that can help them. I mean, when I got hooked into Trek at 14, I went to the library and got books to learn more about it, etc.
6) Shinzon's convoluted motivations. It made way more sense to destroy Romulus to me than Earth. I finally get that Shinzon wanted to prove himself Picard's better by doing something the Romulans hadn't been able to do. But I just didn't buy his beef with Picard. Needing his blood to live, I understood that, but this need to supplant him, I didn't really get. It wasn't Picard's fault that he was created or mistreated. His beef with the Romulans was more immediate and visceral. Earth as target again? Boring. If you got to attack another Federation world, how about Vulcan? Or take it back to Galorndon Core? (I did like the Shinzon/Picard dinner scene in which Shinzon portrays himself as a liberator. I wish they had played up that angle more. It would've made him a more complex and interesting character. The whole 'one man's freedom fighter is another man's terrorist' thing. But they decided to go the mutated, Snidley Whiplash route with him.)
7) B-4. First of all, how did they detect him a quadrant or something away? Why did no one mention Lore? Lastly, B-4 was annoying and took away screen time from the rest of the TNG cast.

The elevation of the Remans over the Romulans. NEM was billed as a Romulan film, but yet we got very little of them. Instead we got the Remans, a race we had never heard of before. I didn't mind the Remans, but I think the focus on them at the expense of the Romulans hurt the film.