Joomla 2.5 was released yesterday, and our 1.7 templates will be upgraded during the next 1-2 weeks. The most important change for those templates that have a built-in slideshow is the modification of line 25 in js/verysimpleslideshow.js. The original line:
if(i > 0) el.set('opacity',0);
must be modified to
if(i > 0) el.setStyle('opacity',0);
With this modification the slideshow will work in joomla 2.5. Other necessary (but not so important) modifications will be included in the updates.