That is indeed what I'm finding regarding hovering over a numeric value field. A regular, let's call it traditional maybe, scroll wheel mouse, will change the values perfectly, but the trackpad and Magic Mouse does not. And scrolling to change values is a real time saver for me.
Thanks for the info regarding dragging on the text next to an input field. That really helps me a lot, but as you say, it isn't consistently implemented, and also doesn't work anywhere in the Develop Persona where I do most of my work.
Now, if this a bug or a shortcoming in the software, should I post it to the bugs subforum or the feature request subforum? It's strange that this isn't a well known issue though, or maybe it's strange that I insist on using a Magic Mouse!