I remember an article about an architect who lost his mental visualization, he had no problem performing mental rotation puzzles. Can't seem to find the article, unfortunately. In general, from reading a lot about this a few years back (when I found out "seeing a picture in your mind" is not just a metaphor...) it seems aphantasiacs don't have any difficulty with any kind of mental task.

Edit: here's the article, rotation stuff is in the 2nd paragraph on page 2.

http://web.archive.org/web/20120615154334/http://discovermag...