We have been running on SQL2008 Standard edition (not R2) and recently upgraded our hardware to a relatively massive machine with two 12 core processors and 256GB of memory. Although we planned to upgrade to SQL2012 soon, we are seriously considering pushing it off until extended maintenance expires on SQL2008.
As it turns out, Microsoft didn't add a cap on memory and processor usage for Standard edition until SQL2008 R2. So if we want to upgrade and use all of the resources we currently have available, it will be a considerable cost increase to license 24 cores on Enterprise edition. That said, the server is definitely overpowered at the moment. We could upgrade and stick with Standard, but it would still be a pretty big increase in cost to license up to the 16 core cap on Standard and we would be limited to 64 GB of memory.
Up until now, the only thing delaying our upgrades was the time to schedule the work, but I'm really having a hard time justifying the extra cost based on the features that upgrading makes available this time.
--Andy