The newcomer to the HTPC Video Card recommendations list, the Radeon 5750 is, like the larger cards it replaces, not a card that was likely made with HTPCs exclusively in mind. It is not a huge card, but it isn't a small one either, so it might not fit in small mATX cases. It also has a larger fan than the Radeon 4670, although depending on the model it may not necessarily make more noise.
Even so, the Radeon 5750 has its benefits. For one, it is great at 3D, which means those who wish their HTPC to do double-duty will be extremely pleased. In terms of performance, the Radeon 5750 can drive any type of video or 3D game at high resolutions, except system-killers like Crysis or Arma 2.
What ultimately makes the Radeon 5750 a good card for an HTPC is that it provides outstanding performance with a minimum of fuss. Reviews have consistently shown that it produces less heat and thus produces less noise (as the fan does not have to run as quickly) than any of the current full-size video cards, which is a good thing for an HTPC card. The only real issue is the $140 dollar price. That isn't bad, but it is much more expensive then the Radeon 4670, so HTPC users will need to decide how important it is to have a cutting-edge card.