Other wise it is similar to Millipede. To increase density, they can move the R/W heads and the media. I've been following this for a while, I have exchanged e-mails with Tom Rust starting back in 1998. Like with fusion, it seems that this has been just a year or two from commercialization ever since...

They have had working prototypes for a long while. I suspect that the problems have more to do with reliably getting it into production.