When does it hang? When trying to access the hard drive? When launching the app? Do you have it running all the time? You can try updating MacFuse in your system preferences and allow it to look for beta updates.

I haven't really used active copy. Tried it and it seemed slow for me as well, but I really didn't mess with it a lot. I use Chronosync to copy files from my iMac to my plug. Works great.

I usually just quit the pogoplug app by right clicking on it in the menu bar and choosing quit. That ejects the drive.

Hope this helps.