I have Fusion running on an iMac with 10.9. I haven't tried my other VMs, but in Fedora 17, my mouse started behaving strangely after the update to 10.9 on the host. It's difficult to click on menu items and drag windows. It's like the hotspot on the mouse cursor isn't in the right place. In addition menu items behave strangely while moving the mouse over them. Menu items not under the mouse become highlighted intermittently. I'll have to try Windows VMs too. Not sure who's API is at blame that needs an update to fix it but it's fairly unusable in it's current state for me.
-edit: in addition if you just hold the mouse down over the window frame, the window starts to move. It's like the window coordinate system changed slightly and that makes the mouse behave incorrectly. Quick check on a Win32 VM and it doesn't appear to be a problem. Unsure why my Fedora VM has an issue.