I liked it.  Quite a bit, actually.  My expectations were very low -- I just rewatched the first three films, and they were even better than I remember them being, particularly Raiders.   Plus, while I think that Spielberg and the '80s are the best combination since peanut butter and chocolate, I haven't liked most of his films in well over a decade. 

 My first apprehension with this film was Janusz Kaminski, Spielberg's cinematographer (who has a very distinctive stlye, which was one of the contributing factors in Spielberg's creative downfall).  I was afraid he'd shoehorn his usual aesthetic into the film, which would have been completely out of place (though I think it's been out of place in pretty much every Spielberg film since Saving Private Ryan, but I digress).  But he was actually able to tone himself down (for the most part), and did a good job of mimicking the look of the first three (again, for the most part).  Spielberg did a pretty spiffy job himself, emphasizing longer takes during action scenes rather than the more fashionable super-quick-cut style.

 Then there's Harrison Ford, who seems to be getting gruffer and gruffer as he ages, and losing some of his charismatic appeal.  He was in peak form here, and seemed perfectly at home with the usual assortment of fisticuffs and stunts despite his advanced age.  The rest of the cast was just as good, even Shia LaBeouff (I know, I'm as shocked as you are).  It was also nice seeing Karen Allen back as Marion Ravenwood, though I wish they had at least tried to keep the fact that she's in the film a secret (she doesn't appear until at least 40 minutes in).

 Don't get me wrong, it's far from a perfect film -- it's easily the slowest of the four films, and probably a tad too long as well.  And despite Spielberg's claims to the contrary, there's clearly a lot of CGI in the film.  A lot less than your average summer blockbuster, but it is there, and it is noticeable.  Also -- without going too far into spoiler territory -- there's a lot of sci-fi stuff (particularly in the third act) which feels a bit out of place within the context of the Indy universe (there's a difference between the mystical stuff from the first three and... well, you'll just have to watch it, I don't want to spoil anything).

 It's definitely the weakest of the four films, but not by much -- it's actually fairly close in quality to the two sequels.  The reviews seem to be really mixed so far, so your mileage may vary, but I thought it was quite enjoyable -- the type of rollicking adventure we don't see nearly enough of these days.