Let's start with the bottom line: I very much enjoyed this movie, and I definitely recommend it. It provides everything you hope for in a Marvel superhero movie, including more humor than I had expected. Benedict Cumberbatch turns in as strong a performance as you would hope, never breaking character and always burning with his usual intensity. All of the other leads--Chiwetel Ejiofor, Mads Mikkelsen, Rachel MacAdams, and Tilda Swinton--also deliver good performances.
I never looked away, I was never bored, and I had a good time. You can't ask for much more than that.
Having said that, the film has one big structural flaw: it rushes to its ending and in the process skips what should have been a significant amount of improvement in the powers and character of Stephen Strange. I don't want to spoil any of the plot, so I'll say only that from the first encounter between Strange and the antagonist, the film moves too swiftly and skips parts I would very much like to have seen. It feels almost as if the first cut ran two and a half hours, so someone said, "Hey, this is a minor character, so trim back to two hours." If that longer version exists, I'd really like to see it.
If you're a fan of the Marvel superhero films, or if you just want a fun movie with a lot of action and special effects, go see Doctor Strange.