Well, I'm probably not the most objective audience member, as I've really enjoyed all of Judd Apatow's films.
This is pretty much par for the course. If you hated Funny People, you might like this more but not be over the moon. If you liked/loved that, you'll most likely like this. If you liked Knocked Up, you'll probably like this.
One thing I can say is that whatever Apatow's faults are, at least the guy is honest. While both main characters have their problems, I think Rudd's falls more on the side of unlikable than Mann's, and the writer is clearly turning the mirror on himself without regard for his own image. The brilliance of making this a family affair is that one imagines most of these scenarios and arguments having played themselves out in one form or another in the Apatow-Mann household.
The direction may not appear at first to have become more sophisticated, but there are a number of smaller, quieter moments that show growth. A brief scene following a meeting with a school principal could have been mawkish but simply leaves the viewer to enter the heads of the main characters to find satisfaction.
I laughed a lot, mostly out loud. But as I said, I'm susceptible to Apatow's brand of humor. The only elements that didn't work for me were Charlene Yi, and a running gag about LOST that feels a bit shoehorned in as it continues. And with the latter, it wouldn't surprise me if this was something drawn from Maude Apatow's own life.
John Lithgow and Brooks were great, nuanced support. Jason Segel and Melissa McCarthy were funny but pretty much what you'd expect at this point.
Rudd tends to be a sympathetic guy onscreen, which offsets how selfish and foolish his character is written. Mann is a treasure who seems to be in danger of some kind of backlash, which would be said because she's still never gotten her due. Her not getting a Globe nomination for this is a fucking joke, even if in many respects she's playing herself. Her timing is impeccable and I love watching her react as well as her outbursts.
If this is going to be considered an adapted screenplay because of the pre-existing characters (which is a lame qualification), then I think I'd probably find room for this on a ballot. Original is a little tougher this year.