What characterizes an excellent presentation?

There is no definitive answer, of course, but there is one minimum requirement:
That is… to communicate your content within the allotted time.
No matter how excellent the presentation, if you cannot finish within the allotted time, the vital content will not be communicated.

PRESENStick is a presentation support device which prevents a “time-over” situation.
Input the number of slides and allotted time and the device will automatically calculate how much time you may use for each slide.
When the allotted time approaches, the emitted sound and vibration will urge the speaker to advance to the next slide.
The speaker may also manually pause, advance, or return to a previous slide.
Using the remaining slide count and time as a base, the device will recalculate the allotted time for each remaining slide.

That is precisely the world which PRESENStick seeks to promote.

PRESENStick creates the best situation for both speaker and audience.
The device is great for those who dislike public speaking and for those silver-tongued speakers who go off on tangents.
It helps ensure that the required content is communicated within the allotted time.
It facilitates a presentation satisfactory to both speaker and audience.

The parts list, circuitry, and source code are open to the public.
https://github.com/takjn/presenstick

The breadboard prototyping protocol is also open to the public
https://github.com/takjn/presenstick/wiki/Prototyping