Before anyone starts reaching for their pitch-forks, Avengers: Age Of Ultron is a very good film. As a Marvel film, it's probably a little less than that - but only thanks to the high bar they set themselves - but as a popcorn movie and a blockbuster (not the dirty words some think), it's a thrill-ride.
Inevitably though, there are some flaws. Comic book purists will inevitably complain that some of their favourite characters have been messed with, fans of threats and death might suggest there isn't enough doom for a sequel, and amateur editors will see it as rushed in places. All are pertinent complaints, and all deserve reference, especially since some of them actually impact the logic of the plot.
With so many plot elements to tie up and new characters to throw into the mix, Joss Whedon's sequel drops the ball a number of times. It's entirely forgivable, because the action and the pace just about make up for it in the first 2 or 3 viewings, but over time, there are some problems that just might take some of the gloss off for you.
They are the plot-holes, narrative contrivances and downright mistakes that you would hope a project this big and this expensive might have ironed out before release. Sadly, that wasn't the case.