Creating good user interfaces there is really a science in itself. The reason is that many programmmers (as myself) are focused on the engineer part and less on how things are accessible for user.
If you know Joel Spolsky, he presents very good reasons why user interfaces are complex. The quote that is the most important in my oppinion from all topic is this: "A bunch of tiny frustrations, and a bunch of tiny successes. But they added up. Even something which seems like a tiny, inconsequential frustration affects your mood. Your emotions don't seem to care about the magnitude of the event, only the quality."
Using various interfaces, I am likely attracted with Mac OS X/GNOME interfaces: they stride to be minimalist at first and try to hide to user most of options. Also, they emphatize with automatically apply UI and the buttons are tend to be "reversed" compared with older applications on Windows. The reason that most persons are right-handed persons and they will more likely hit the right-most button if they will not look at what is it.
Some reasons of being minimalist as interface is to not overwhelm the user from one side, and picking defaults that (almost) always work on the other side. The reason of applying automatically the interface is great that you will mostly change your options and you will save a step by clicking again on OK (if you not click wrong on cancel and have a frustration). Another reason in NaroCAD at least is that some options are really frustrating when you pick a wrong checkbox and close. You will have to open again options, to go back to that specific Options' page, and uncheck your options. If you click a wrong option and you see the results right away, you don't lose the "context" by closing the dialog and move back.
So based with tha good faith and following the giants in UI design, I've applied most of that knowledge on NaroCAD. Today I've just finished an automatically applying non-modal Options dialog. In this way you can test if your Solver options (the component that is used for autoaligning your mouse point to various references like corner points, paralel lines, paralel planes) without going back and forth. Also the dialog have in bottom-left corner an Undo/Redo arrows pair, so if you get wrong some arguments and you just found that the defaults are better, you may use the defaults right away applying the Undo. Also the Undo will say which page was changed when the undo is applied.
The dialog of Cut Preview was also changed to be asynchronous also, so you can rotate right now the scene as much as you preview the cut.
You may download the latest build from here.