I just installed the Events Calendar, and added one event, which is next month. I used an Events List widget, and it doesn't list the date. Plus, the tooltip is messed up (it renders HTML code). The long calendar displays the current month, but unlike the calendar setup page, it doesn't have any options for "next month" and "previous month." Since the one event I added is in September, the calendar is completely blank. Additionally, the big calendar does not appear where I put it. I put it below the text on my "Upcoming Events" page, yet it appears above the text.
Finally, and this is surely related to the various problems above, my site, which used to have both valid XHTML and CSS, now has numerous XHTML and CSS validation errors, all of which appear to come from the Events Calendar plugin.
I'm using WP 2.6 and Events Calendar 6.4. An illustration of all of the problems above can be found on http://www.vantagehoa.org/upcoming-events/