You can force AA for W3D Viewer by creating a preset in the ATI Control Centre. Essentially you set the AA controls to maximum, not "let the application decide" as per default. When set up properly, you can enable this preset when you're ready to take a screenshot - all programs, including W3D viewer will suddenly have some AA. It doesn't appear to completely eliminate the problem, but it does improve the look of screens somewhat. You can also set anisotropic filtering in the same way, which will greatly improve the look of the textures. Make sure to switch it back afterwards, it can cause some problems with 3D apps (lags my 3DS Max to hell) and games.
I hear Nvidia has a similar setup for their cards, so you Nvidia users shouldn't have much trouble adapting this.
Now if only there was some way to get shadows in there...
Edited by Nertea, 04 April 2006 - 06:31 AM.