Ok. Opened presentation with 15 slides (downloaded it from web), where are pictures and text with background is present (no effects in elements though, except of slide change effect). And didn't noticed no differencies in appearance, when launched it in PowerPoint 2007 and in LibreOffice Impress. Maybe using PowerPoint isn't worth until it has problems with monitor detection? Esp, if you don't need to share the presentation with others with the file, and only for demonstration, so, using LibreOffice maybe is a pretty good solution. Since It has almost same possibilities :)
