What's the best software to run on a dedicated HTPC? ideally it should be totally standalone and quick to startup - e.g. an appliance for the purpose of this question, I'm not looking for PVR capability, just playback. I'm looking at XBMC live, but wondered what others are out there that can do the same sort of thing.
edit: additional info - I currently have an original modded Xbox running XBMC - it's fantastic at what it does, but it doesn't (and cannot) do HD playback apart from upscaling. so I'm looking at an alternative hardware platform that is at least as flexible as the Xbox/XBMC combo. I'm hoping a 9300 chipset MOBO (e.g. ASUS P5N7A-VM) with HDMI out will do the trick with XBMC live now that it supports hardware decoding on NVidia chipsets...
UPDATE:
I'm definitely sticking with XBMC front end and am building a Myth TV backend to go with it. I originally wrote this having already bought the ASUS P5N7A-VM and I hadn't anticipated the massive uptake and availability of ION based boxes, so if I was doing this from scratch, I'd still go with XBMC Live, and running on a ION Nettop such as an ACER REVO, ASUS IONSTAR or build from a Zotac Ion Mini-Itx board.
However, I've stuck a Celeron 430 Conroe-L CPU in it, underclocked it, and undervolted and it hardly produces any heat :) and works like a charm