Wow. Quite real. Other dust devils have been noted in full resolution images: http://www.lpi.usra.edu/meetings/lpsc2009/pdf/1799.pdf
, and /or http://www.space.com/missionlaunches/08091...ust-devils.html
Meteorology-sensed dust devils as well as imaged one are discussed in a recent JGR (for those so inclined and with access). Abstract: http://www.agu.org/pubs/crossref/2010/2009JE003413.shtml
Anyway, I haven't heard of one (or, now, several) in one of the low-res horizon movies. And I like your enhancements to show details in the structure. Here is a contrast-enhanced version of all 32 frames. The dust devils show up late. You also see cloud and cloud-shadows moving around. I omitted time stamps, but it is about 50 sec per frame.http://www.met.tamu.edu/mars/phx_enhanced_141_1FBC3R2.gif
Edit: well this is sad--the activity claims to be a deliberate dust devil search, which explains the low pointing compared to normal horizon movies, which look at clouds. So it should have been seen, oh, 540 sols ago...