I saw an advance screening of this film last Thursday night, and it was pretty good. Very family friendly humour and a strong cast including Ben Stiller, Robin Williams, Owen Wilson, Dick van Dyke (legend!), Ricky Gervais, Steve Coogan, and Kim Raver (Audrey Raines from 24).
It's really along the same lines as Jumanji, and has a decent story (pure fantasy of course), good lead performances, some pretty funny scenes, and great special effects.
My only criticism of the new trailer is that it gives too much away (as do all trailers these days). The original teaser trailer was much better for showing a flavour of what the film is like but without giving away important plot points.