I don’t like comparing Seesmic to Twitter because they are vastly different. However, everyone’s first response to Seesmic is "This is Twitter with video!" It is a valid metaphor. Once into Seesmic though you will see that is a time-shifted conversation. Do not time to keep up with the public timeline! It is not synchronous so Seesmic is NOT video chatting. It is asynchronous. While you are watching someone’s video response a few other people may be making responses. While you are watching those responses the actual timeline slips further into the future while you remain in the past to participate in the conversation of your choice.
I have compared Seesmic to being in a party. You hear the noise of all the conversations. Your mind can half-heartedly follow a few of the conversations. And you can commit yourself to one or two. If you step out of the party The Conversation continues and when you return you just step in at that moment. You don’t ask people to rewind or go watch the security tapes to try to catch up. You simply rejoin The Conversation. Same with Seesmic.
Warning! Seesmic is addictive! There are no timezones because Seesmic is on World Time. It never shuts down. You will get to know people from countries all over the world.
If you think you are ready for Seesmic, drop me a comment, firstname.lastname@example.org, or Twitter me. I have a few invites. First come, first serve. Of course, bribes, links, and contributions to my Vasectomy Campaign (see also) are appreciated!