I have tested Symantec Endpoint Protection (version 11.0.5002.333) this week and did not run into any issues. I had setup Symantec Endpoint Protection to auto update daily and scan all hard drives daily. I had put some test date on a hard drive which Symantec Endpoint Protection was able to scan with no issues. I will use this AV software on my WHS 2011 build until Microsoft updates Microsoft Security Essentials to run in WHS 2011 and SBS 2011.
No impact to accessing you media library from remote access? I have seen this is a problem with a couple of packages.