Hey Keith do you still feel this way, four years on? (Hope I am outside the statute of limitations for asking for things which have already been taken off the table. If not it’s a fair cop.)
I personally would like the option of italic and underline toolbar buttons. Probably because they’ve got them in Final Draft so it’s become a reflex to reach for the toolbar, then go “oh, no use the keyboard” which wastes a precious 1.5 seconds, or else click through the fonts tab which wastes a precious 1.8 seconds.
There will be NO toggle button for bold, italic or underline in the toolbar for 2.0. Instead, they’ll be in the format bar, which goes just under the toolbar, as in Pages.
(By the way, you do know that 1.0 has B/I/U buttons in its rulers, right? If you show the ruler - cmd-R - the buttons are there. Not the greatest place because they appear twice if you’ve got two editors open, but it should see you through until 2.0.)