well you figured out it how better than I, since I used SendInput and didn't bother with any WM_'s etc. So I found at least 20ms per window, before and after the click. Wow is using GetCursorPos but handling mouse looking is more difficult since WoW will try and use SetCursorPos on each background window and expect it to go to the centre of the desktop, so you have to be intelligent about that . Supose I can fine tune now based on this, and with SendMessage you'd be certain of WoW processing the up click straight away so you could eliminate any post-click-delay.

Well part 2 I'm just saying its possible to get it to accept a click straight from the background, direct from the mouse, which isn't neccessary since there is TweakUI and same deal in Vista but those are annoying to have running for general use. I hadn't figured out the WM messages would cause a click anyway so it was the first thing I was looking to solve.