Mercilessly savaging the comic book version of The Mandarin was absolutely correct. It put the comics in proper perspective.
Concluding the Tony/Pepper story with all the Iron Man suits blown up, the shrapnel removed, Pepper handwaved back to normal and Stark announcing he's a changed man? Well, the notion that growing up means abandoning juvenile comic book notions of adult empowerment (complete with total ability to kick ass on the playground!) is pretty obvious. Given Tony Stark is a billionaire with movie star looks and whatever woman he wants just brings us commonplace fantasies about unlimited wealth and sex.
This is not an emotionally compelling conclusion. It may not be scifi, so you might claim it is more grounded or something, but that doesn't make it any more realistic. Not in any significant meaning of that much abused adjective, anyhow.
The visuals and design simply are not as effective as in previous Iron Man movies. There's nothing as imaginative as the whips. And the scene where Downey appears to be charging the Iron Man suit from a car battery goes beyond having a light touch, into making fun of your material.
Although the conclusion is not as satisfying as the makers would want, the journey however is quite amusing. The dialogue is fresh, the score is effective. I rated the movie above average for these reasons.