First things first: The Avengers (or Avengers Assemble for those expecting some Diana Rigging) is a whole heap of fun.Whedon clearly knows the material inside out, keeping the plates of homage, geekery, whip-smart scripting, generous character development and relentless action spinning together with poise and elegance. The simplicity of the plot - essentially Thor's Loki returns to earth to add annihilation to his CV - makes way for an expansive arena in which the superheroes' egos, sensibilities and cultures clash in the most satisfying and jocular of ways. To this end, Whedon wisely delays the nerdgasm spectacle of the group's harmonious kick-assery till the end, instead allowing us to witness the Avengers' unravelling loyalties and shifting paranoia with one another. There's more than enough room for the individual franchises to shine here, from Hemsworth's fish-out-of-water shtick to Downey Jr.'s endearing smirk, but it's Ruffalo as Dr. Bruce Banner (and mo-capping as the be-greened one) who emerges with perhaps the most depth of backstory and nuanced performance. I'd be happy to censor any misgivings about another Hulk re-boot were Ruffalo to be involved. Elsewhere Johansson and Renner wring as much as they can from underwritten parts. Predictably the film tends to sag whenever things get too serious, but the script's wisecracks and visual gags are what really make it sing - the playful Whedon magic once more. So a success then? Commercially, at $2.5b worldwide for the entire Marvel Cinematic Universe to date, I would say so. It's a pure popcorn experience of course, nothing more, but it's also a deliriously giddy and gratifying watch.