Do I need to change my ICA (intermediate) back to the previous one later on?
No you do not, you can keep the existing intermediate certificate installed and do not need to switch back at a later date.
Do I need to reissue all my GlobalSign certificates?
No you do not, in fact you do not need to reissue at all, simply follow the process guide here to replace the ICA (intermediate certificate). For some platforms, such as Tomcat however a reissue might be a more straight forward route.
I've got a SHA1 certificate, will the same process work for me?
As an end user you may need to clear the CRL & OCSP cache on your local machine/browser if presented with an affected certificate. This can be done easily by following the instructions here, the CRL & OCSP cache is slightly different to that of your browser.
When are the Alpha SSL and Cloud SSL ICA's (intermediates) being delivered?
We are actively working to deliver these ICA's (intermediates) as we speak, and are hoping to have them ready within several hours (from 21:45 UTC). Update: You can now retrieve these from the troubleshooting guide
I can't seem to apply the fix on IIS, what else can I try?