Working fine in my 10D. Judging from the amount of "empty" MuVo carcasses being sold on eBay (mine included), there are hundreds of the 4gb drives being used in cameras.
With all these salvage drives being yanked, sold and used, you'd think by now someone would have posted something like "it damaged my 10D" or the like; I've yet to see anything like that, except for this one guy on eBay, who has a financial stake in slamming the competition, saying "mine is better than yours."
I did notice the following comment in an article by Wired:
Because the MuVo2 appears to be hard to obtain, several people have tried dismantling iPod minis for their internal drives. Unfortunately, the drive in the iPod mini appears not to work in digital cameras, though there have been reports of getting it to work in the MuVo2 and some CF card readers.
One of the contributors to the iPoding website dismantled an iPod mini and, after a series of unsuccessful experiments with card readers and formatting utilities, rendered the drive inoperable.
"Oops," the writer said in a post. "If anyone knows of a reader/adapter which definitely supports the 4-GB microdrive, please let us know."
