I just use a star to mark what I want to do today. Are you using this feature for something else?

Microsoft To Do does this. There's a "add to today" button. Dead simple.

My workaround is a Saved Search called Today that includes anything set as Next Action with a star. Kludgy, but it works.

Yes! Currently I set the Due Date field to Today and select Today filter to see only Today's tasks. Different color for stars would do it. For example one click on the star would turn it on (as it does today), second click would turn it red (like in Gmail) and automatically set the due date to Today.

This a very useful feature, I've been dreaming about it since the very first day a used toodledo. Stars, priority, folders, hotlists etc they are just not good enough to very easy and fast create a short list of the next tasks I must take care of.

Why not just use stars for this? Are people using stars for something else and therefore need 2 different single-click-tags?

Yes, I also use a combination of current features to indicate that it is on my Today's List. A simple way of doing this would be to enable different color stars. I would then just use red stars for today's list. If this were combined with one of the above requested "Batch feature selections" you could select all of Today's tasks and change the star or other field to Today's list. Definitely useful suggestion.

Yes! I've been using a star, next action and high priority combination for this in the hotlist. Hotlist has those non-optional priority and due date criteria. I use the stars to flag tasks that I can just do, without any dependencies. Some kind of "Do Today" field that works like the stars would work for me. Or just tie the hotlist to a hotlist checkbox instead of all the existing criteria. But I suppose some people find the current hotlist useful as is.