Anyway, it's an interesting experiment; giving songs for the fans to remix like that. I can't see the copyright-crazed majors allowing their chattels to do something like that (i.e., if Radiohead did that, it'd probably come with a special rights-managed remixing program which ran only on your Trusted PC™ and let you give a few play-once low-bitrate Windows Media copies to a handful of friends before self-destructing), but I think it makes sense for indie artists. Mogwai probably have more to benefit from a fan-made remixes of one of their songs floating around the MP3 nets and being played by laptop-glitch DJs from their Ableton Live-equipped iBooks than most artists; much in the way that Björk has to gain from all the bootleg remixes of her songs floating around.
As for the album: haven't heard the whole thing yet, though it sounds good. It seems that the detour into Radical Jewish Thrash Metal that was My Father My King was just that, and the album is a progression from Rock Action; if anything, it's more introverted and subtle, though in a good way. In places they're starting to sound a bit like Sigur Rós, though.
Speaking of Sigur Rós, I also picked up their Sigur 1 - Sigur 9 single, which came with a DVD of videos. The one for Svefn-g-englar is not bad, and quite apt; it basically has people dressed up as angels moving about in slow motion around an Icelandic landscape, under a volcanic cliff and a featureless off-white sky. (The video was a US import, where they are released through MCA/Universal, which is presumably why it's a Region 1-only DVD.)
(Interesting that Mogwai hail from Scotland and Sigur Rós hail from Iceland. I wonder how long until a post-rock band emerges from the Faroe Islands, a point roughly halfway inbetween.)