For a Marvel film, this is one of the weaker ones. Both Benedicts are great actors, the visuals are also great (though not as colourful as I would've liked) but the problem lies with the story...
The plot is not even bad, but it wants to do funny; it wants to do strange; it wants to explore the characters in an emotional level; it wants to have a theme of "time"...... But none of them are done well.
Personally, I would've liked a stranger movie with even weirder effects including a consistent theme with "time". And showcase how much more of a human training in the mystic arts has made him.