Please don't spread anti ATI FUD, granted ATI support hasn't been very good in the past but neither has NVIDIA, the difference now is that ATI is now supporting the opensource movement by releasing their documentation. This action should be rewarded and the company should be supported not shunned by us.
Unfortunatly statements like "as a word of advice, stay away from ATI" don't help the cause or send the right message to the company from the opensource movement. The company is helping out in the linux development, as a real world example, please take a look at the progress of the xf86-video-radeonhd, it's amazing what Alex et al are doing.
I've setup a lot of mythboxes and use ATI cards in them, the xf86-video-ati now supports tv-out out of the box, maybe a little xrandr tweak here or there, but nothing too special. I personally use old school Radeon 7xxx cards in my boxes to play HD content to SD TV's using s-video, works great, so do the multitude of friends machines I've setup using the same video card. I have mates doing HDMI on Radeon HD3300 integrated graphics using radeonhd, granted, no sound over hdmi, but you can get it from the onboard optical out.
I heard you say "research your hardware" a number of times through the podcast, this includes your video card, please apply your own words of wisdom, do some research before telling people to not to support a company who is supporting us.
Keep up the podcast, I enjoy hearing about the antics of other MythTV users, I too remember my first setup four or five years back and the antics of having to stay up all night to figure out how to install gentoo, the tears shed getting the PVR-350 driver compiled and tv-out enabled, and having to send patches to the dev list to fix bugs in nupplevideo player to support x86_64.
Oh yeah, they were the days... It's way too easy now
Cheers.