I've already covered Slideshare during Cam23 and my thoughts haven't really changed. They are contained in an earlier blog post.
I have seen a few presentations made using Prezzi recently, some good and some really bad! At worst they gave me motion sickness since people seem to think that because it has all of these fancy new features, they must be used.
Even the ones that were slightly calmer were still a little busy. I understand that it's a good tool for drawing parallels between points but people seem to take this to the extreme. I was watching a Prezzi presentation last week and the speaker had used multiple pictures to illustrate her points. I found myself more trying to work out what the pictures were trying to represent than listening to her presentation! Also, I find that if the equipment is a little outdated then the presentations run very slowly which makes them look a little clunky. Maybe I'm old fashioned, but I think that the traditional PowerPoint presentations where you can look at something static on the screen at any point in the talk work better. I find too much of my time in Prezzi presentations is taken up following the text/images around on the screen rather than paying attention to what the speaker is saying. It seems to be designed for people with very short attention spans.
Having said this, there are some good examples of the technology out there. Some people have really got to grips with what it can do but I'm not sure it will ever win me over. I know the same was true of PowerPoint when it first came in. People used many special effects just because they could and the result was cluttered mess. Hopefully things will calm down with Prezzi but as of the moment, this isn't one for me.