A fan of the first film, I no less was a bit trepidatious at blind-buying this Blu-ray. Having seen it, I can only assume that the naysayers didn't see or didn't understand the first film, as this met my expectations and then some. Those who "got" the first film, should know from that that the movie isn't about the monsters. While real - this isn't some disappointing dreamscape where the fantasy, alien, or supernatural element is a figment of some persons damaged psyche - the monsters are used as metaphor for a narative that's more profound than simple action or horror.
New setting, new purpose, with a bigger budget. And the special effects and sound are blockbuster - you won't want to experience this on some wimpy tablet or cell phone via over-compressed streaming or download. Throw the BD up on the big screen (that's what high fidelity, high def is for!) with full blown surround and a powerful woofer. The sound alone is one of the more visceral I've heard lately and just makes the movie all the better. And the video easily holds up even projected at 100 inches.
But if you have any expectations at all, I'd suggest you go in thinking "The Hurt Locker", rather than expecting some new twist on the likes of "The Mist". With expectations out of the way or the right expectations in place, you shouldn't be disappointed.