In the last meeting a student asked why the "new" tabs (gadgets.Tabs) don't work while the old (legacy) tabs do work. Here's an explanation:
Currently the gadgets.* namespace and opensocial.* namespace work only in what's called the sandbox: http://www.google.com/ig/sandbox
It is for experimenting with these new APIs.
They will be available in the "real" iGoogle only in late summer.
Which means that if you think you really want these APIs, try to play around with the sandbox and get it to work there. You can submit something that works in the sandbox and does not work in the real iGoogle because by late summer it will.
But for most of you, using the "legacy" API works fine.
Also, don't forget to read the previous note I wrote yesterday here.