In addition to what Pyscogeek wrote, the rectangular and elliptical marquee tools will always align to the pixel grid, and you can nudge them a pixel at a time or 10 pixels at a time. Similarly, the pencil tool is designed to fill whole pixels only.
And with shapes and paths even without
Snap to Pixel enabled, you can still fairly easily align them with the pixel grid if you know a few basic tricks and use some simple math:
- As mentioned earlier, snapping to grid/guides can be one way to place/move/scale paths to whole pixel units.
- You can also use the rectangular marquee (with the info pane open and ruler units set to pixels) to lay down guides in the position and size you want a shape/path to be.
- If you're not zoomed beyond 100%, then your paths and shapes automatically snap to the pixel grid regardless.
- If your path/shape is a little off, just free transform it. You can then set the height/width/X/Y to whole pixel units. If your height/width are odd, then just set Y/X to half a pixel, or you can just use a corner or edge reference point.
Lastly, in CS6, you have the
Snap Vector Tools and Transform to Pixel Grid option in General Preferences. This makes it even easier to have your vector paths align with the pixel grid.
So while Fireworks might be more suited to pixel-precise design, it's still fairly doable in Photoshop with a little practice.