If you're after pixel aligned shapes and are considering Photoshop CS6, my advice is to buy it. There were many positive changes from Photoshop CS5. Two new options that replaced all the previous pixel snapping options found within the tools. It's so much nicer now.
For me, the biggest change in CS6 is pixel snapping being moved from the individual vector tools to a global setting, with the catchy title of Snap Vector Tools and Transforms to Pixel Grid. It’s hidden under the general tab in preferences, but is actionable, so you can enable and disable it with a keyboard shortcut.
With pixel snapping off, Photoshop’s nudging behaviour is similar to how it was previously — nudging is connected to the zoom level. If you’re zoomed to 100%, then nudging will move one pixel. If you’re zoomed to 200%, nudging will move 0.5px. Keep zooming in and the increments get smaller:
100% — 1px.
200% — 0.5px or half a pixel.
300% — 0.33px or a third of a pixel.
400% — 0.25px or a quarter of a pixel.
500% — 0.2px or one fifth of a pixel.
600% — 0.1667px or one sixth of a pixel.
...and so on, all the way up to 3200%, which nudges 0.03125px.
With pixel snapping turned on, nudging always moves one pixel. And by one pixel, I’m talking about one pixel, relative to the current position. A point that’s located at 50.5px will move it to 51.5px if nudged while pixel snapping is enabled.
Photoshop CS6 also contains a feature called Align Edges, that's a little different, but related.
Align Edges, found in the options bar, ensures the edges of the layer are aligned to the pixel grid. The non-edge contents of the layer are scaled without snapping to the pixel grid (this is important to note). In some cases, sloppily drawn vectors can be fixed simply by turning on this single per-layer option.
I've written more about them both here: Vector shapes in Photoshop CS6