There was a time, not so long ago, when I would have not felt comfortable seeing R-rated comedies like this one. However, films like Wedding Crashers and The 40-Year Old Virgin (a film I was initially freaked out about, but quietly went to see anyway) showed me that those films tend to be the more funny comedies.
Knocked Up is no exception. There was some very funny scenes in that movie and, as in the case with these types of movies, all the funniest stuff involved sex, drugs, or a whole lot of bad language.
However, it also has heart and I was amazed at how well the romantic stuff mixed the crude stuff.
Overall, I thought it was a worthy follow-up to The 40-Year Old Virgin (and I definitely felt more comfortable seeing this film than the last one).