At first I was like: hmmm. But then I was like: okay, whatever.
Tom Cruise is not an inherently bad actor, and update films staring him are not inherently bad. War of the Worlds was actually okay. The Mission Impossible films were also pretty cool. I think the problem here is two-fold: (1) Fark Movie-goerstm don't see that Cruise's personal lifes craziness never compromises his competency as an actor; and (2) you need to let go of the notion that At the Mountains of Madness is going to be a pure adaptation of the original.
MoM was written almost a century ago, at a time when the geography of the antartic was almost completely unknown. A lot of HPL's atmosphere of dread was extrapolated from that fact alone. In 2010, we have not only mapped the whole surface of the continent, we have penetrated the ice with ultrasound and radar images from space. It's not an unknown place to us. In as far as we still find it scary, the reason is because it's uninhabited and oh-so-cold. Dead cities and shoggoths? Sadly, no possibility.
If I were Del Toro, I'd be making this a history piece, kind of like Jackson's King Kong. Sure, we know this place doesn't exist in the real world, but we'd be happy to watch Cruise in a waist coat and woolen overcoat autopsy the Old Ones and follow the shrill cry of the shoggoths to the valley beyond mount Erebus. And there I would diverge from the original tale.
See, MoM didn't have a lot to film. You could make a short film of maybe 45 minutes about it, but no way could you fill a feature length pic with two geologists wandering around cold and ancient stone passageways studying heiroglyphs. At least, you couldn't do it in a way that would get enough bums on seats to turn a profit on the investment. No, my bet is that we'll see not only shoggoths, but also deep ones (who don't belong), and Old Ones capturing some hot yound chick from the party, just to give the protagonists something to go after. And the shoggoth will be different.
At the end of MoM, we finally read about a living shoggoth, barrelling up an ancient hallway, pulverising albino penguins in its wake. It's really the one true monster horror of the whole story. You can't pull that off in film, even if you're Del Toro. Expect a pseudo intellectual action flick with shoggoths and lots of snow. Expect a three act structure with conflict between party members and a girl who needs saving. Expect more than just the one shoggoth. Just don't expect a retelling of the MoM story that is even 10% as faithfull as the Lord of the Rings movies.
In my opinion, if I wanted to see MoM as HPL intended, I'd just re-read MoM. If I want my wife to get a foothold in the Mythos (and I do, but she reads too much bloody Jodi Picoult), then I'd take her to Del Toro's version of MoM.
And I'll enjoy it too.