hmmm brings up the question again, that on earth is the "deinterlace" setting doing? Defaults to off, and I have it set to off - when I turn it on, there is a noticeable CPU hit. But I don't think the CPU is doing deinterlacing in the off position as the CPU usage doesn't suggest that. Also, most of my sources would be progressive (TV torrents) but smaller than 1080, so its just scaling.
Either way, the bit rates of these source vary WIDELY from fairly low compression to high compression, and the bit rate is usually much more important to the CPU usage (unless you're comparing 480i with 1080p!) as this can be anywhere between 1Mb/s through 15Mb/s depending on how the show was ripped...
I will have a think about switching to 1080i, but it could be difficult getting a modeline for that which works with my TV (have had alsorts of probs!) - but it is likely I will end up increasing the load if the CPU really is doing this... as I say, most of my content is progressive, so it will end up having to interlace it
In any case, even if this is a solution for others, it is unlikely to be for me because as I mentioned, the jerkiness even occurs on the screen saver pics... and interlace isn't relevant there... damn