Resampling without filtering like that is really fast.

Oh, sure, but I'm referring to something else. If you have a slow-moving object rendered on a 160x120 pixel screen, it may move 1 pixel, say, every 8 frames. Now scale this up to 1280x960, and your object will be 'jumping' 8 hardware-pixels every 8 frames, instead of smoothly moving 1 hardware-pixel every frame.

Of course, that can be an artistic choice, as long as you're aware of it.

I'm not sure I follow. It's all logical pixels. Let's say our example is a galaga-type game and the moving object is a missile fired down toward the player.

The goal is to have the missile move 1 logical pixel per frame regardless of hardware resolution.

At higher resolutions (without commensurate higher PPI) the logical pixel will become physically large and begin to look pretty weird/potentially undesirable at certain viewing distances. But the missile should always still move precisely 1 logical pixel per frame. It will pass the same amount of background art each frame. It will approach the player just as fast. etc

The example you give (1 pixel of movement per frame) is the only case in which there is no difference. Anything faster or slower will show smoother movement by using all the available hardware pixels.

In my example, the larger screen has e.g. 8 times the number of pixels horizontally to show movement in. Instead of waiting 8 frames and skipping ahead 8 hardware-pixels, you can render the sprite 1 hardware-pixel further along every frame.

I still don't follow why you're saying "waiting 8 frames". But I think I get what you're talking about -- essentially interpolation.

The problem would come from anything other than simple movement of a static sprite. If there's some much as a wispy smoke trail animation off the back end of the rocket as it flies through the air, the sprite data isn't going to give you any indication where those particles should be waving about during your interpolated frames.

You'd model the rocket exhaust as individual particles or suffer the blocky animation. But it's not rocket science :)

'Realm of the Mad God' works this way, with the added affront to purity of having rotated pixels. I think it works rather well: http://www.youtube.com/watch?v=hpMdFFxFbY4