There are two different "flavors" of OTF fonts, those with TrueType outlines and those with Postscript outlines. If you double-click an .otf file in Windows Explorer you'll get a preview window, the top of which includes some basic information about the font including the outline flavor. OTF fonts with TrueType outlines will work with Revit. OTF files with Postscript outlines (most OTF fonts) will not.
However, that last part is not exactly true...
I have a typeface that originally came in the form of Postscript-flavored OTF fonts. I converted them to TTF fonts, installed them, and worked happily for months. At some point I had to re-build my workstation and in the process accidentally installed the OTF fonts instead of the TTF. To my surprise, all of the existing annotations that were set to use this typeface displayed and printed correctly with the OTF fonts installed. I could edit text, change tag labels... it all seemed to work! The only thing I couldn't do was actually see the name of the typeface in the list of available fonts, e.g. I couldn't create a new text style and assign that font to it.
So... it seems the only part of Revit that doesn't work with OTF fonts is the font selector list. Perhaps in Revit 2018 that limitation will be removed.
