Indiepath: I'm of the opinion that if you are making a puzzle game with pre-redendered art that a projection matrix won't really benefit the customer (who won't experiment with res changes) and also it may deform the carefully made art a tiny bit.
I think you're missing the point of the fact that an LCD (which is now outstripping CRT in the home) scales to your game res really quite badly, causing blurry graphics and artifacting, where the average CRT would not. This is because LCD scaling methods are really terrible. Some are better than others at this.Basically, if indiepath was to use his projection matrix to make a full screen windowed mode window at desktop res, the LCD would not need to scale, and the graphics would actually be much crisper as the graphics and projection matrix would be handling scale up, not the LCD.
This is preferable visually, but I for one won't be doing it because it is literally too much bother for the casual market and of course be a bit slower. It would not be a lot slower however.