I should start off by saying I'm a little biased, since Baby Blues was a part of my childhood. I started reading this comic strip in the newspapers when I was three years old and just started learning how to read. Rereading it again made me realize how funny the jokes are!
It is not a comic strip like Calvin and Hobbes or Garfield (although they're among my favorites too) because it's not trying to appeal to kids. It's more like The Family Circus where it combines humor with nostalgia about parenting (I can't relate to being a parent exactly, but raising my baby brother I could relate to the baby jokes). Unlike Family Circus, however, it's prime focus was the humor (I'm not trying to stab Family Circus; the FC creator even said that his goal was to make parents smile rather than laugh).
They don't have as many story lines as they did in the 90's to early 2000's, but their focus is still the same. The humor has gotten a little bit staler since Hammie became a kindergartner, and the jokes have had some repetition, but it still manages to get a good laugh out of me now and again. Besides, Kirkman and Scott aren't "new parents" anymore, so it's probably harder to find new jokes from raising kids. At least it's not like Garfield, which has long past the point where it should have ended.
The children have set personalities, but they have some character development as well. Zoe went from being a colicky baby -to a misbehaving toddler- to a bossy big sister. Hammie went from being a quiet(er, compared to Zoe anyway) baby, to a curious toddler, to a rambunctious little boy finding his place as the middle child. Wren has grown from the "new baby" to about one years old, and is the toughest and quietest of the three (except when she's crying of course!) Darryl and Wanda are the dad and mom who try to find a balance between staying "stress-free adults" (yeah right!) and being parents. They always try to be the best parents: strict, not too mean, not too much of a pushover.
There was a short lived cartoon by WB. It didn't capture the spirit of the strip that well and pushed the main family into "secondary characters" while the Bittermans (who are not in the comics) took on as the main characters. I would recommend watching it, but be aware that unlike the comic it's target audience was teenagers.