User just sent me an ai file they couldn’t open (because we don’t have an Adobe Illustrator license). Found that Gimp does the job nicely.
Just needed to set the resolution up a bit (to 600dpi) to get a nice hi-res image to forward on for the user.
Best thing about the GIMP http://www.gimp.org is it’s cross platform Window/Mac/Linux.
Update: As per comment from Juan. Inkscape also can open ai files. I tried it and found that it gave edit access to the ai image.