We are about to implement Groupwise throughout our organisation and bit the bullet by squeezing in the upgrade to 2012 before we migrate. Possibly risky, but we weighed our options. I have to say that the upgrade process is an absolute dream. I updated multiple domains and POS, webaccess all in a couple of hours. And it all came up working first go. Excellent!!

Anyway, one of my techo's discovered that if you use either MSWord (We run office 2007) or OpenOffice (I run LibreOffice 3.4) it will often crash groupwise when sending email, especially with pictures.
It's not a show stopper for us, but thought I'd log the feedback. We still do have Outlook 2007 installed until we migrate so not sure if that causes a conflict. However, I think it's probably a more fundamental bug in the Groupwise client 2012.