ArcGIS Desktop does not export to a specific Adobe Illustrator file format structure. However, there are no known issues opening ArcMap-exported AI files in Illustrator versions 9 or 10, nor in versions CS, CS2, CS3, CS4 or CS5 (11, 12, 13, 14 or 15).
As Adobe completely changed the text engine in Illustrator with the CS release, text displays as 1pt size; however, there is a workaround to update the text strings to the CS, CS2, CS3, CS4, or CS5 engine. See the corresponding Esri Knowledge Base document in the Related Information section below for more information.
Be sure to also export to AI in ArcMap at a resolution divisible by 72 to preserve accurate line weights and text sizes. See the link to the corresponding Esri Knowledge Base document in the Related Information section below for more information.