Having used a variety of platforms, I have found that there are often some technical hitches, or challenges which need to be solved before using the system. Some of the challenges are not directly related to the web conferencing technology itself, but web conferencing in general.
As with all training, it is important to consider where the training will take place for the end user and how it could impact on their participation.
Audio:
There are some things to consider about how audio will impact your participant. The first is their environment. Do they have speakers or headphones for their computer, and does their computer have a sound card (which some may not have in some workplaces)?
If they are going to be listening to the conference at work, and they don't have a headset, will this impact others around them?
If they may want to talk, or are required to talk during the web conference, do they have a microphone working? Perhaps there is background noise which...