I use it and it has relatively few bugs. It has been highly recommended by Patrict Norton and Leo LaPorte on This Week in Tech, the #1 rated podcast on iTunes. It is capable of converting many kinds of video that Quicktime cannot. It is much, much faster than Quicktime and much more configurable, allowing you to tweak the audio and video encoding parameters, choosing between H.264 and MPEG-4, bitrates, framerate, resolution, audio sample rate, etc.
That said, you can create incompatible videos by choosing parameters which are outside of Apple's iPod spec. And there is an issue with playing Videora-converted videos on the v1.1 iPod update on 60GB iPods. They play fine in 30GB models. I expect this to be fixed in the near future.
If Quicktime will convert the type of video that you have and you don't care how long it takes, how big the file is, what the quality settings are, etc., then Quicktime is probably a good choice for you. If all of the above doesn't apply, take a look at Videora iPod Converter.
