I got a PackIt last year for my daughter when she was in kindergarten. It was alright, but I would't buy one again. The velcro was in really bad shape well before the school year ended and would come apart really easily. We were able to make due until the end of school, but then it went in the trash.
The PackIt is also pretty heavy, which may not be important if you have older kids. Since my daughter is younger we put her lunch bag in her backpack or she would lose it. The weight of the PackIt plus whatever else she had to carry made her backpack extremely heavy some days.
This year my daughter is using a regular insulated lunchbag with two of the Rubbermaid Blue Ice packets and it stays much colder. We're in Florida and my daughter is in the afterschool program. I pack her lunch at 7:00 in the morning and a good portion of the Blue Ice is still frozen when we get home at 5:30 or 6:00 in the evening.
FYI - if you do get a PackIt, do NOT fold it up when you place it in the freezer. I found that if I layed it flat it worked better. There were times when I folded it and put it in the freezer and pulled it out the next morning and it wasn't frozen all the way. That only happened a few times when I forgot to put it in the freezer until later in the evening, around 10:00 or so. Anyway, if you lay it flat it freezes faster.