Most name-brand tablets have excellent graphics capabilities and support either wired (HDMI, VGA, etc.) and/or wireless (Apple TV, Google TV, Roku, etc.) video output. The total cost of ownership of a good quality tablet is less than that of a PC, and, as "appliances", they are far more reliable.
<br>
I've spent a lot of time searching for a paid program for my iPad that would give me a fraction of the capabilities that OpenLP has to offer and have come up blank. Keynote can do slides and some multimedia, Vjay can do videos only, and others, like iOpenSongs, can manage song libraries (primarily for musicians and not for presentation sake).
<br>
I think this is being dismissed too quickly as I expect there to be growing interest in this as PCs, regardless of OS, become more and more passé.