I used to work at JC Penney Portrait Studio, back in my college days. Now, while I had a photography background -- most employees did not. And yes, they always booked the appointments too close together. I'd always look ahead on the nights I was scheduled and strategically schedule "phantom" appts. -- made up people that obviously wouldn't show up, therefore, giving me more time with a larger group. Maybe not in the best interest of the company, but you know what... my pics always had great sales and isn't that the point? Anyway, mostly what you will pay for at a "chain" like Sears, Target, JCPenney, etc. -- is the background and lighting. The rest is a gamble. The posing, the way the kids look, etc, is really variable depending on who takes your pics. Picture people has always done great shots of my friends two children, but I've had mixed results from even them. Always long waiting time which is challenging with four kids in a too crowded space filled with breakable frames and such within their reach... they have always been rushed with us too and my favorite photos from them are ones I've insisted on posing myself. I also don't like having to hang around the mall for an hour to get my pics back... not that waiting three weeks is super either.
We always do a family portrait in the fall (six of us). I had been frequenting Target with the kids lately because they have no sitting fees and you can choose any of the poses they take as your "package" pose if go with that particular coupon. They are also cheaper than the other places around here. Well, we went there for our family photo this year and it truly stunk! She didn't get a single good picture.
So the moral to the story is that you never know what you'll get at a place like this... by "this" I mean, Target, Sears, JCPenney, Wal-Mart, etc. If you frequent them and find a good person, then you can try to go on their shift but other than that, it is a gamble. Just know though, that you do NOT have to buy anything and you can probably even demand a refund on your sitting fee (maybe you'll only get credit though for a return visit)... but don't settle for pics you don't like. You can always have them re-done. I know it's a monumental pain, but that's what I did last fall. I walked right out of Target and wrote down the name of the girl who took our pics and I refuse to go there when she's working.
Anyway, with the Kodak machines nowadays, if you ever take a great pic of your child, it's easy to make reprints of them.
I echo the sentiment that using a local photographer will produce the best results, but if you don't have the luxury of spending that kind of money -- as they are usually more pricey... you'll have to try the other places. They aren't horrible, you just never know what you're going to get and if you go with that in mind, you'll be best prepared. Good Luck!