|Preparing for an in-place upgrade. @ NFL I own the rights to this? :)
Word to the wise: if you plan on doing an in-place upgrade from server 2012 to 2012R2 be prepared to re-create all your OS level network teams. If you upgrade a Hyper-V host and your teams were used for switches, be ready to re-create those as well.
I don't recommend doing an in-place upgrade in the first place for reasons like this, but I figured I'd give it a shot on one of the hosts in my lab. Every OS level network team was wiped out, but easily recreated.
Other than this I haven't found any other in-place upgrade issues... yet, and that's why I'm always hesitant to recommend the practice. It's rare you do find what the issue are until the become a problem.
Any issues you've encountered? Leave 'em below!