The response seems to be very mixed, as expected:
"The good news for Ford fans is that Indy may be older and greyer, but there’s still a spark to his repartee." -- John Harlow, The Times more...
"Between a series of stunt-driven set-pieces, implausibly linked, the film gets bogged down in wearying talk." -- David Gritten, Daily Telegraph more...
"Welcome back Indy. Lord knows we’ve missed you." -- James Christopher, The Times more...
"Despite the genuine excitement, and one blinding flash of the old genius, this new Indy film looks like it's going through the motions." -- Peter Bradshaw, The Guardian more...
"Indiana Jones and the Kingdom of the Crystal Skull gets swamped in a sea of stunts and CGI that are relentless as the scenes and character relationships are charmless." -- Kirk Honeycutt, Hollywood Reporter more...
"Spielberg clearly got enormous pleasure employing a lifetime's worth of skill and turning out wave after wave of smartly done stunts and effective set pieces." -- Kenneth Turan, L.A Times more...
"Indiana Jones and the Kingdom of the Crustal Skull feels simultaneously self-conscious and self-satisfied, as if a little warm glow of past glory will soothe our bumps and blows from the clumsiness of the script." -- James Rocchi, Cinematical more...
"The magic is still there, only you have to work a little harder to make yourself believe this time." -- Leah Rozen, People Magazine more...
"A lot of the picture veers uneasily between solemnity and slapstick and 47 different genres." -- Michael Phillips, Chicago Tribune more...
Some of those "bad" quotes seem harsher out of context, but the general consensus is definitely to lower your expectations. But I'm hoping a lot of those reviewers are middle-aged (i.e, they weren't kids in the 1980s) and can't enjoy it for pure childish nostalgia.
I haven't hyped myself up expecting something on par with Raiders Of The Lost Ark, fortunately. Hell, I may even agree it's the weakest of the four films... but it's just great to have a childhood hero back on the big screen. And none of those reviews lead me to believe it's going to be a Phantom Menace-style let-down. I think it'll be enjoyable, particularly if you're a fan and child of the 80s. We'll see.
Now if we could only get Ghostbusters 3 into production...