I'm doing some testing, but I could not find the option of having a meeting without the attendees of that meeting needing to download the application and see only in their browser. My client has very weak internet, so that would be a problem.@
The Add-in is only required if you are sharing your screen or uploading a PPTX file. So, you client shouldn't be required to download/install the Add-in for Connect and is should run within the Flash Player in their browser of choice.