I found, that problem is conflict with NextGen Gallery. When I deactivate NextGen, feed works.
For your site I can see the contents of the feed (but without events), but at my site I do not see it (www.divadlonasantovce.cz/?em_ess=1). Have you set something else? Or just only isntall ess plugin and it shows the feed? The lack of instructions is frustrating. I never have found instructions on how to set ess or where to find feed, etc.
