I do a fair amount of presentations, and I have to say Keynote has made my life in front of the big screen a lot easier. Of course, a good remote is really a near necessity when doing presentations, and after trying many over the years I've settled on the Keyspan PR-Pro3 Remote.
It is very Mac friendly, and requires no software at all. You plug in the included receiver in any USB port on your laptop, and turn on the remote. They instantly pair, and you are ready to go. The remote gives you forward and backward controls that work with Keynote or PowerPoint and a button to blank the screen at any time. You also get a two-button wireless mouse, you can be up to 100 feet away from your laptop and maintain remote control.
The remote also features volume control, and includes a bright red laser. When you are done, the USB receiver snaps inside the remote, so you have one thing to pack. The remote runs on two AAA batteries, and they seem to last a long time. It's pretty sensitive -- manipulating the mouse will take a bit of practice.
The remote can also control slide shows in iPhoto, and even switch tracks in iTunes, although it's not a function I have a lot of use for.
There are a lot of presentation remotes being offered, and I have tried many of them. The Keyspan is really excellent, and while it lists for about US$100 it is commonly available for about half that online.
If you do a lot of presentations and crave more than a forward and back button, take a look at the Keyspan unit. I don't think you will be unhappy with it.