Gaikai is letting the public try out the fruits of its efforts: Demos of Mass Effect 2, Dead Space 2, Spore and The Sims 3 are all playable from within your web browser. That is, if you have the bandwidth -- we don't, apparently. (Granted, we're on gratis Wi-Fi here at GDC.)
You might have better luck at home: You can visit Gaikai's site where you'll be prompted to launch Mass Effect 2. "Just wait and if your connection quality to our Server is fast enough," instructs CEO David Perry, "one of several pop-up designs will appear."
Additionally, taking a survey about the service will grant you access to the Dead Space 2 demo. Spore and The Sims 3 trials can be found here and here, respectively.