Jeez, that was quick. As previously teased, an Overlord II demo has gone up on Xbox LIVE Marketplace today. To add the file to your Xbox 360's download queue, click here the US version and here for the UK demo.
Is the 360 not your primary gaming console of choice? We're told the demo is in the works for the PlayStation 3 and PC, and that it should be releasing sometime next week. Seeing as how Overlord II doesn't launch until June 23, you should have plenty of time to try before you buy either way.
Having passed up the original Overlord even though I love the series' core concept, I for one will be grabbing this demo the next time I power up my Xbox 360. So, after E3, if I'm lucky.