Recently Illustrator received Distance Guides (can be disabled in Preferences > Smart Guides > Invoke Distance Guides), thanks to this request: http://illustrator.uservoice.com/forums/333657/suggestions/34302196 (it uses Opt/Alt, not Cmd/Ctrl)

For some reason the color of text in these is black — while the lines use the one set for object guides (magenta by default today). It makes it very hard to see when working with dark designs.

Dimension Tool uses magenta color for the same text... I think it should be either magenta as well, or a separate option should be used to set the color.