Two complaints so far ...
Having switched to Mac I was excited to see an OSX DDO client.
Playing with it on my 2011 MacBook Air (i5/4gb/256gb) I found that performance is pretty good, though I have only played for an hour or so to this point. Over the years having played with many different PCs, the performance did seem to be more than good enough to enjoy an evening of DDO.
Two issues relating to the keyboard are real issues though.
-- 1) Keymap changes are not saving for the next session. Any changes made are lost when restarting the client. Since I like use the keyboard to attack and strafe, functions that have no default keyboard equivalent, this is pretty annoying.
-- 2) When the OSX Keyboard preference for 'Use all F1,F2, etc. keys as standard function keys' option is set you can not type in chat or anywhere that typing is possible. Deselecting the option does allow you to type.
Graphics performances was decent. On UltraHigh the frame rate was low, which I expected. The unexpected part was floaty text appearing dissolving with background elements (monsters, grasses, etc). Lowering the graphics setting down to High got rid of that issue.
Previously I have played DDO using the Windows client under Parallels. That works well and is a good option, if you already have Parallels installed for another reason since it costs about $60 plus a Windows license. I'd rather use an OSX native client though, and look forward to some of these issues (mine so far are annoying enough to make the client unworkable for the long time) get resolved.