As good as OpenOffice is getting these days, I have a personal issue with Impress (and, indeed, presentation software in general, such as the ever-popular Powerpoint).
My slideshows are very often not presentable in a bullet-point format. Indeed, it seems slide after slide of bullet points can get a little tiresome. Thus, for my talk at Barcamp Brighton this weekend, I felt much more like going with Inkscape. Unfortunately, it's not too easy to load inkscape files as a slideshow... or so I thought.
Enter Inkview. Appearing in the latest versions of inkscape, you pass it a list of SVG files on the command line, and it opens a window with some basic presentation controls. It's pretty basic, but it's just what I was after. There's no real way of sharing a common 'master' background among SVG files apart from the traditional copy and paste (well, as far as I can see), and if you want to keep your sanity you'll want to make the filenames correct so you can just call "inkscape slides/*.svg", but it works.
I much prefer it to Impress. This is probably because I don't really do presentations too often, but... that's not really too important. If you feel like a bit more graphic flexibility next time you make a presentation, you should probably at least give it a passing thought.