I don't have the definitive problem nailed down, but there are certainly early symptoms of "something" not quite right with the DDO Client operating on Windows 10. Here's a couple things so far after upgrading to Windows 10:
1. In Windows 10 desktop with the DDO Client icon available on screen, if you right click and "Troubleshoot Compatibility" and use suggested fix dialogue along the way, you will end up with a non-functional client, and potentially need to uninstall the entire DDO package including Akamai, and reinstall the entire DDO package from DDO.com.
2. When logging into DDO for the first time after a Windows 10 install, and using the default Windows security programs, and specifically Windows Defender, you will typically get a popup warning when the DDO Client tries to connect for the first time in Windows 10, which will ask you if you are clearing the login for either Private or Public network access, or both. I don't know if there is any limitation or bug that occurs if you choose one or the other, or both, if you are simply using your normal home network. However, after logging in with Windows 10 and trying both the "Private" only selected, and another time trying both "Private" and "Public" selected -- in both cases the game is acting buggy as if double loading, with double echos for audio along the way, and lagging out very badly. Anyone else perceiving this "double" issue for Windows 10? One other symptom I am seeing, is that the Yellow icon in top middle of screen for latency shows up at least once every minute, sometimes more often, and yet my Ping and connection are no better or worse at the time I was connecting to DDO in contrast to any other given day. Jumping and hanging in the air - has happened several times now, game just stalls with me in mid jump.