What is the best platform for A/V presentation over the internet?

My boss has asked me to look into a software/platform for the purpose of giving a presentation over the internet, rather than fly me and a bunch of gear to the location. I’ve been researching a bit, but don’t have any first hand experience with these products.

Basically, what I need to do is broadcast my screen (or a powerpoint presentation) and have audio along with it. It can be with computer audio, or phone conference, but I’d need some way to get questions and feedback from the audience.

I’ve been looking into Citrix GoToMeeting, Webex, Acrobat Connect, and BeamYourScreen. It should be coss-platform, because I would prefer to use my Macbook Pro. I would like opinions from anybody who has experience with these, or similar products, to help us decide which way to go with this.

Oh, and we will only need this sporadically (just once to start) so MS SharePoint server, and expensive suites are out. We’d like to keep it closer to $100 or so.

Thanks!