If you read the post, the following things were pretty clear:
(A) The hardware was designated LONG before he even considered trying Linux.
(B) The cost to purchase other hardware is prohibitive at this point in time.
My problem is the user tried MythTV with hardware that was documented would not work very well and then blamed MythTV and Linux that they didn't work very well.
As long as Linux's community is more content to groan and whine and point fingers rather than fixing problems, Linux is in trouble. Whether or not they particularly like ATi, Linux will not grow by insisting on only certain hardware - first because it needs as much compatibility as possible, and second because it causes just such bad experiences like this when linux zealots are overenthusiastic and tell people that their system will run find and be ultra-happy with Linux when it quite possibly won't be.
The other problem I see here is the sheer number of linux zealots outright flaming the guy for telling what his problems were.
Let's face it, the LAST thing you want to do is tell someone who eventually you'd like to become a linux user (and they claim they want everyone to use Linux) "you suck", "you shouldn't be allowed to have a computer", "you should just get a Tivo", "you're stupid for buying hardware X", or anything else of the sort. You only contribute to their negative impression of Linux by doing so.
Anyone with any marketing sense will at this point remind you: one upset customer is worth 100 happy customers. People may tell one or two friends about their good experience at Restaurant X, but they will tell EVERYONE about Restaurant Y where the food was burned, the waitress was rude and late and caught making out with the busboy rather than checking her tables, and the check came back with a 20% gratuity already added on despite the crappy service. The same holds true for this: instead of this guy having one experience and saying "oh well, I guess it didn't work out" he's tried again and again, each time being told "ok they fixed it now, it'll work", each time it doesn't, AND he gets flamed by idiots and linux zealots for even bringing his bad experience up.
In the long run, this kind of behavior has only hurt the Linux community, and Linux zealots really need to realize this. You've driven away a ton of potential users.
Downmodding someone who's had a bad experience with a Linux distribution or a piece of Linux software isn't going to help, and neither is badmouthing them.
Now for my personal issue:
The documentation I've found, for any flavor of Linux, is (in descending order of maddening potential)
(A) poorly written
(B) contradictory
(C) arcane (as in, has a bunch of steps and scripts that would work fine... as long as NONE of them has a problem, in which case good luck finding out how the problem occurred or how to fix it)
(D) written for the wrong version (instructions for Ubuntu Feisty Fawn no longer worked correctly on Gutsy Gibbon, no longer worked correctly on Hardy Heron, etc)
(E) simply not present.
That's a problem. That's at least as big a barrier to entry as insisting people build a new box for their Linux purpose, rather than being able to use existing hardware that they probably purchased long before anyone even asked them to try Linux out.
And just to be perfectly clear, and at the risk of repeating myself: you can't go around badmouthing people for having the "wrong" hardware when you are the ones trying to get them to use your software.
No wonder people don't take Linux seriously on the big market. I'm starting, based on the behavior of writers in this thread, to wonder if they actually want people to use Linux or not.