Just want to share my experience so far. I got my notification that the upgraded was downloaded about 2 weeks ago. I had planned to find the hidden upgrade file and convert it to an ISO file to do a clean install from. Unfortunately, after a long weekend, 2 weekends ago, canoeing and camping; the update decided to install itself. So fast forward a few days after the canoe trip weekend and I come into my office at home to check some things on my computer. BAM.. It's running Windows 10!.
At first, I was pretty frantic that my computer was going to be messed up and I was going to have to redo my windows partition etc. Fortunately, that has not been the case. My computer only need a few restarts to finalize some updates after the upgrade. It's running as good, if not better, than before. My only quirk, so far, is my function keys on my laptop keyboard are not working. It's not a big deal to me as I always use a wireless keyboard and mouse anyways. Also, my password keeping software won't load up properly without right clicking and running as administrator. Other then that, it's been problem free as of now.
So far, I'm actually really enjoying Windows 10. Cortana is decently useful. There's a good mix of window's 7, and 10 for me. I was ok with windows 8, but never liked it enough to upgrade. Microsoft's Edge browser is pretty nice also, although I still prefer google chrome.
Here a quick pic I snapped to show my discovery the night I found my computer upgraded itself.
I hope everyone else has as good of an experience as I have so far. As always, make sure you back up everything, multiple places if you can. Otherwise, here's to not feeling completely left out by apple not supporting the mid 2009 13" MBP's with bootcamp 5!