I have a Linux-based file server at home which I access from my Windows machine through SMB. I have been running Windows 8 Consumer Preview for ~6 months straight without any issues.
I've recently upgraded to the Windows 8 RTM (Pro), and now performance has gone from stellar to abysmal. I am experiencing extreme loss of speed (previously able to stream high resolution video, now has trouble keeping up with loading small audio files), as well as sporadic loss of connection.
Update: After doing some more research, it seems the issue is that my network connection is capped at ~10mbit downstream. I am using the builtin RealTech gigabit ethernet adapter with a Cat5 cable and a Netgear gigabit router. What in the Windows software could cause this cap, and how would I go about fixing it?