I'm just back from seeing it. I liked it, though it definately has it's share of problems. The visuals are great, but the story is very predictable and the characters, both good guyus and bad, are rather boring. There's zero chemistry between the main characters, and I didn't really buy their romance for a second. Also, the movie feels very unfocused, as if there's almost too many ideas, the whole, let's call it, "Rihanna episode" is entirely unrelated to the plot, could be cut without missing anything, despite taking a big chunk of the movie. It's a fun episode, but still.
But there's plenty of fun concepts, great designs, and the interdimensional bazaar heist part near the beginning was really clever and fresh. I actually regret it's set at teh movies beginning, it would have made for a more interesting climax than the rather by the numbers gunfigh/race to disarm a bomb.
Anyway, despite teh problems, it's fun and worth seeing on the big screen. Just don't expect it to measure up to the Fifth Element.
Thanks for letting me know what you thought about Valerian. I agree about the love story. In fact, my major gripe with the movie was the love story, although I should say that I generally don't care much for love stories in any movie. It often feels like it's there for no reason, perhaps just there to pander to a focus group (like when game devs think that *every* game needs multiplayer or something).
With that said, I have seen some good portrayals and the love story in Valerian could have been done so much better and more subtle. Now it was the weakest part of the movie and all that "you know you like me"-talk from Dane Dehaan just got tedious. His character felt quite bland and, actually, I thought that his love interest Cara Delevingne outshone him in the acting department and I don't often think about whether an actor is good or not, I only think about whether I like the character or not. Nice to see somebody famous who "tries to be an actress" and actually succeeds. Rihanna doing her little show felt like pure eyecandy, but I liked her role otherwise.
I liked your Twilight-link and reading the comments was almost as fun as seeing Michael Sheen chewing the scenery (Twilight is so anemic that doing so was the only way to get any nutrition, haha).