I recently used my iPhone as a remote control to move between slides for an on-stage Keynote presentation.

This is one of 2 ways you can now use an iPhone/iPad to give a presentation. The first is to run the presentation in the device itself and connect it to a screen via an Apple TV (or a cable if you are sitting around a conference table). The second, is to use your iPhone/iPad to control a computer via WiFi or Bluetooth.

I used the latter. While it did work there are 3 glitches, one of which is a big one:
  1. Both your iPhone and your computer need to be hooked up to the same WiFi network, which requires some fiddling with technology. For some reason Bluetooth failed to connect the devices. So it is different from using a standard plug and play Logitech remote that works always in a second. Budget time to make it work.
  2. You move between slides by sliding the screen, which is a movement that is a bit hard to do with one hand. I would have preferred it when the volume + and - buttons would have been allocated to do this, like in the camera application. 
  3. And here is the big one, your remote can get stuck in the middle of a presentation. It happened to me twice where I had to wait for some buffer to clear before I could move on to the next slide. Not good when you are standing in front of a big audience.
Because of number 3, I would hold off using an iPhone as a Keynote remote for very important presentations.