I'm using version 1.8 of the plugin. Thank you very much for creating it!
I am using nivo slider in the header of my 2012-derived theme site. I noticed that the slider was resizing the page after the images loaded. I wanted to avoid this, so I used the CSS to hard-code the size of the slider in the header..
Unfortunately, 2012 is flexible width, so I broke smaller screens like mobile devices!
I came up with an approach that fixes this, using a hidden div with a margin that makes it maintain aspect ratio, even as the screen resizes. I would gladly offer my modifications back to the author or others if they would find it useful.
You can check out the slider on my site if you'd like: http://songoftheroad.com