User friendliness of ‘floating’ WYSIWYG editors such as Medium and Summernote ‘Airmode’

Currently there are some WYIWYG editors (medium.com and summernote airmode)that provide a 'floating' toolbar to edit the text. I.e. The user highlights the text and a toolbar shows up above the text allowing the user to change the text to bold etc.

While I think this is a very convenient way of editting text as it cleans up the interface and allows us to reduce the amount of buttons to reduce unnecessary affordances, it is still hidden from plain sight. Only after selecting text it shows the toolbar.

How convenient do you think this type of editor is for a first time user?