I don't like Webex's web conferencing product. Nor GoToMeeting's. I get invited to online demos using these tools all the time and I find both products resource hogs that are slow to get going, and that make it hard for me to take notes on my PC while watching a presentation. But what really bugs me is that I know the people who invite me to these demos are paying big money for these apps. They shouldn't have to. Screen sharing and conferencing is becoming a commodity feature. See all these stories for examples.
There are two more products entering this market being shown here at the DemoFall conference (more stories). The most interesting is DimDim, a free, open-source conferencing and screen-sharing app with what looks like a ton of flexibility. You can share a presentation file if you upload it to the Flash-based service, in which case nobody needs to download any code -- very nice. Or, if you want to share your screen, you (the presenter) will need a small download, but other participants will not. The service also offers video and audio conferencing, or will optionally use a free conference bridge via telephone.
If you want to put your own company label on DimDim, or install it on your entreprise's servers, you'll have to pay to license it, but it's otherwise free when running on DimDim's hosts.
And then there's Yuuguu, another free screen-sharing app. This one is designed more to replciated the convivial office experience for people who are not actually in the office. It's based on buddy lists, like instant messengers, and requires a download to work. But once your work buddies are online, it lets you easily share your screen and do voice chat over the connection.
I haven't used either of these tools for real meetings yet, so I cannot vouch for their speed or stability. But I like what they are doing: challenging big, entrenched, expensive products with new, leaner products and much more palatable pricing models.