It's been in the wild for about a year and used internally at Cisco before then. The main advantage over GNS3 is it includes layer 2 switches, uses way less resources than GNS3 (the ones I've seen floating around are VMs).
I haven't used it but a lot seem to love it. It can do most of the CCIE R&S lab prep. Though not as comprehensive as GNS3 or Dynamics with Layer 3 switches (but you can probably do the same with IOU).
I do, its pretty neat. Only thing that bugs me is that you have to manually type in all your interface connections (using the correct format), but other than that, its pretty great.
Cisco VIRL is coming out sometime this year or early Spring 14'. That is probably what you will want since you will be able to simulate all the OS's Cisco has to offer. VIRL does automate a lot of configurations but you will be able to configure everything yourself. I think this will be more towards people who want more experience in obtaining CCIE Data Center or SP. If Cisco can provide layer 2 / 3 switching in VIRL then this will be the program to use in obtaining any networking certifications.
First time I've heard that they're trying to expand GNS3. Are they also doing anything for newer router platforms? I think that's the issue they're going to run into versus VIRL. VIRL can integrate virtualization, IOS 15, IOS XR and NX-OS. The possibilities are endless, and it's all supposed to be free.