[RussleTop]

Sometimes I find that Omnigraffle doesn't snap to grid cleanly e.g. shapes will be slightly mis-aligned even through snap to grid is turned on.

I suspect that this may be because I have alignment and distance guides turned on which take precedence over snap to grid?

[Joel]

Without seeing the document, I'd bet dollars to donuts that it's the smart guides, they are very aggressive.

[albertellenich]

I've noticed that "snap to grid" seems to apply on a page-by-page basis. If I copy an element from a page with it turned on, I have to be sure I turn "snap-to-grid" on in the destination page before I paste. I'm not sure why snap-to-grid isn't global. Maybe it's just my copy, but I've learned to work with the assumption it's only relevant to the page you're on, not the entire multi-page document I may have created.