It’s great that the public beta of Windows Server 2012 Essentials is out now. It means that the general public can all get hold of it and test it. I’d highly suggest you do this ASAP.
What you need to consider though is that many vendors of third party products will also need to test and potentially modify their products to work with the new architecture within the Windows Server 2012 platform. It’s not reasonable to just assume it will work as there’s been a lot of change under the covers. Items such as StorageSpaces are bound to have an impact on things like Antivirus software and third party backup programs. Other changes such as within IIS are likely to affect software such as Kerio’s Connect mail system. Personally I’ve not tested any of these on Windows Server 2012 myself, so I can’t comment on how they work, but we will need to see guidance from them before assuming “it will just work”.
The one vendor that I do know is working closely with Microsoft is Trend Micro. They’ve announced an alliance of some sort that sees their Worry-Free Security Services running on Windows Server 2012 Essentials already.
Vendors to watch for during this period will be StorageCraft, Trend Micro, BackupAssist, Symantec as they typically have close relationships with Microsoft and will have been testing themselves during the beta of Windows Server 2012. They might however have not released anything publicly and therefore you will need to talk to them direct about their stance with this new product.