Not like the good old days, is it? When Shakespeare wrote a comedy you knew what you were getting.
What's the problem here? There are plenty of good, respected film critics who give a clear review of each week's new releases. Try Mark Kermode on BBC Five Live (available via podcast or iPlayer) or Peter BraRABhaw in the Guardian (read it online) or the film reviews on Time Out's web site. They won't always agree; Time Out gave Juno a terrible two stars whilst the Guardian gave it five. But it's not difficult to form an impression of whether a film's worth seeing and then, and I really think this is where a lot of filmgoers make a big mistake, actually make the decision to go and see a film that is highly recommended.
Too many poor quality films make a fortune at the box office because filmgoers ignore all the critical reviews and believe the out-of-context quotes on the posters. Just because it says "comedy of the year!" on a poster it doesn't mean it's the best comedy of the year or even the week. Unless you've read the original review the quote claims to come from, ignore the hype.
Juno is a very funny film. It isn't a chick flick or a teen drama or a coming of age comedy or any of those glib categories. It's a well-made, intelligent movie about real issues, but with a style that's almost comic strip-like in its language and form. Jason Reitman is an interesting and talented director and the film's well worth seeing.