Glenn, I'm glad to hear that.
Here's something to add to your thinking. Remember that you can drag guide lines off any other line whether that is an edge, an axis or another guide. This makes it a simple matter to locate points in space. If you also add the Protractor tool into the mix, you can add guides at angles to other lines.
Consider the possibilities of this. Let's say you're designing a cabinet with a hinged door. You know where the door needs to be when it is closed as well as where you want it to be when it is open. Maybe the door needs to clear some trim as it opens. You can use guides to locate the hinge line by working off the two locations of the door.
there's all sorts of applications for guides and since they aren't part of the geometry of the model, you can draw them in and delete them at will without affecting the model.
I use guides to lay out the limits of a piece or to work out some dimensions. Since SketchUp's inference engine can see them, it gives tools something to snap to so they can facilitate moves or rotations. They make it simple to lay out the limits of arcs for radiused edges. They also make it easier to draw Bezier curves. Especially parabolic arcs.
Guides can also be copied like regular geometry and you can make linear or radial arrays of guides so you can layout geometry that might be repeated if you like.
They do start to clutter the view a bit so it is good to delete them periodically. That shortcut is handy for that.