I believe this is very different from the spanning/dynamic volume support already present in Windows.

- data is written in 256MB slabs, which also include metadata. Thus the physical disks are readable in any other Win 8 pc, as long as you have enough to form a 'quorum'
- support for parity, mirroring and resiliency
- probably built on top of a new filesystem layer called ReFS, details on which are scarce

This is the work the WHS team was doing for DE v2 when they decided to scrap DE completely from WHS 2011. I hope its will include features such as Single Instance Storage and automatic error correction and detection (the 2 missing biggies) soon.

The goal of partitioning should be (or at least is for me) the ability to wipe and restore a partition without affecting others. Doing it for space/categories doesn't make sense because

1) folders work just as well. If you must, mount a folder as a drive letter
2) sooner or later you'll run out of space while another partition has free space

So what I do is make a OS partition (40-50gb is enough) and a data one. On the data partition are 2 folders - Data and Apps. Then I move my user profile folders into Data, so that all docs, music, pictures are in there. All portable apps go in Apps. Everything else is installed by default in c:\.

This allows me to reinstall Windows or restore an image of the OS partition without affecting my data. I try to use portable apps, and if not (e.g. Visual Studio), reinstalling is simple. Data gets backed up as usual, and I don't worry about data on c:\ since by definition it is expendable.