In response to the reviewer who stated that you can get 8 or 9 hours on a standard minidisc - yes you can, but at real poor quality (in terms of the potential quality MD and Hi-MD can give you). To get that much recording on a standard MD you have to use quite a low bit rate which results in a horribly brittle sound (just as with low bitrate MP3) and is not pleasant to listen to.
On a single 1 gig Hi-MD you can get just under 8 hours of music at the very nice 256 bps and is certainly near-CD quality (the top bit rate currently available is 352 bps, which is near impossible to distinguish from CD, and still allows about half a dozen average-length albums on a single disc).
Yes, it is a 'multi-storage' medium - ie. you can store any kind of file on it. But then again, most storage media nowadays can be used to store anything. If you connect a digital camera, for example, to your PC's USB port you can drag any kind of file onto your camera's internal memory or SD card, even play music files off it whilst connected. There's no reason why you would, but the point is the term 'multi-storage' is not really a big deal.
Don't be fooled by some of the low prices of discs here though - they'll charge you pennies for the disc then the best part of a fiver for delivery! Wish they'd just be honest about what they're charging you for, because there's no way you can justify four or five quid to deliver one of those little things!
Still, regardless of that, I reckon a Hi-MD disc is easily worth around a fiver.