I can confirm that Illustrator's snap-to-grid features are utterly broken and useless in CS3 on XP. I can't test other platforms, but I do recall having seen these same sorts of problems using grids in prior versions of Illustrator.

No matter how you set up your grid, no matter how you use objects, groups, or symbols, it just doesn't work. Any number of methods of dragging shapes can result in points being placed not on the grid. Even the simplest thing like dragging the edge of an object or a hollow point with the hollow arrow doesn't work most of the time.

This is extremely unfortunate too because for the number one design app in the world to not have the most basic adherence to grids is just ridiculous. Many other posts online just say to turn off grids, or use snap to point. Meh.

If you really know the math going on under the scenes, this feature _should_ allow you to design pixel-accurate objects that work the same whether you bring the artwork into Flash or Photoshop. Sadly this is just not the case.

What's worse – it also renders using Symbols on grids useless. You double click a symbol to edit it, make changes to force its points onto the grid, and then escape the symbol… your object is now completely off the grid! It's just embarrassing. Adobe really needs to get their act together.