Greetings,
With regards to this subject, I'm a worthless data point because I don't do much in the CentOS project other than occasionally reply on a few mailing lists... so I'll not be volunteering for the jigdo stuff... but I do want to point out that I have used it on a number of occasions and it is very handy. You can download the DVD and then basically build the CDs from that. Saves downloading 5-7 CDs per release if you want all of the media.
The Fedora Unity project seems to really like jigdo for their distribution and claims that it saves them a significant amount of bandwidth.
I understand that not everyone would use it and that it is hard to get people to try new things but if it was there, I'd definitely use it... although I don't think anyone is saying to switch to it exclusively... and yes getting it working on CentOS requires some packages.
A new up and comer is zsync. I've only read about it and I don't know how useful it is. Ubuntu has adopted that.
TYL,