To make it even better, It would be nice to have an option on 7+ Taskbar Tweaker to show the tooltips, even when the text fits within the button. Right now, it's only shown when the text doesn't fit.

Why would I use such a setting?

That's the way Windows XP works. The tooltip is shown whether the text fits or not. It makes things more predictable, I think. You always expect to see it if you park the mouse over the button.

OK, finally found something that works. It's the ExtendedUIHoverTime you mention. But it doesn't work if I place it under:

HKCU\Control Panel\Mouse\

HKCU\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced\

It works, both for the live thumbnail previews and the tooltips :D

Thanks for your help. It's working perfect now :)

Thanks, I'll try that.

I also found about the DWORD DesktopLivePreviewHoverTime on:

HKCU\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced\

Yea, I misunderstood what "always_show_thumb_labels" does. Sorry about that.

About the speed of the tooltip. Thanks for the tip, but:

I'm using the option: "Hovering" > "Tooltip". And I did change the options and registry keys to make them appear faster. I've tried from anything between 0 and 5000. And it's actually doing something. It's affecting the speed of the tooltips shown by some apps. When I set it to zero, it gets really annoying. But... it doesn't  affect the speed of the tooltips shown by the taskbar buttons. It always takes like 2 seconds. I tried with "Show thumbnail preview" to see if that changed, but nope. Takes like 2 seconds no matter what I do. It may be a problem with my system. I'll investigate and post here If I find a solution.