I am already running the latest build of SM on Server 2012 (non r2) with over 1000 active users. Are you saying that shouldn't be possible? What features or enhancements am I missing by running on non r2?

John,

Running it outside of the system requirements means running it in an unsupported environment.  The biggest thing you're missing out on is the ability for our team to support your installation due to that.  As far as specific tech features or enhancements, I can't comment on those personally.

Thanks, I'll open a support ticket to get more details.

Sounds like you are probably OK with SM and "non-R2" Server 2012. But if you need it, you can buy Server 2012 R2 OEM on ebay in sealed packages for $50-$60, including COA label. I've purchased these several times from different ebay vendors without problems. FYI, my personal ebay rule is to always pay with credit card in case there are any issues.

We’ve run SM on Server 2012 (non-R2) without issues before.

If you volume license Server 2012 you’ll get access to both the non-R2 and R2 version. So, you won’t need to purchase another license.