The summary includes one of the major differences, the kernel. Wheezy (and sid as of now) has 3.2, this aptosid release has 3.9. The aptosid kernel stays very close to vanilla mainline with the latest stable/important/security patches and suitably tuned for most desktop users.
Another major difference is the installer (and it's live system) which brings a coherent set of packages to start with and some initial configuration which helps make it more suitable for use as a sid system such as disabling the installation of recommended packages by default. The initial aptosid system is a clean sid system, such as you can get from debootstrapping, without the pain of bootstrapping or the baggage accumulated by starting from a stable system and upgrading it to sid.
As a result of not being tied to the Debian kernel and debian-installer it can also often adopt features ahead of Debian itself without breaking compatibility with sid. Examples have included ath5k support for a fully Free wifi experience, insserv support for parrallel starting of initscripts and support for installing on EFI systems. Of course it doesn't support everything d-i does nor all the architectures of the Debian kernel.
The aptosid manual is great and covers an awful lot of material from setting things up to maintaining your system, guiding you to keep a supportable system in the unstable environment. It's available in 14 languages at the moment.
The artwork of course is also aptosid's own, changing with each release. Beauty is in the eye of the beholder and of course you can pick other art from the Debian packages or your own images for wallpapers ... though I never bother.
Finally there is a community which wants to support those running sid and a "fix.main" section of the aptosid repo which often includes some "hot-fixes" for issues which have cropped up in sid, helping to protect it's users, sometimes briefly just waiting for the next debian mirror push and sometimes for issues which end up staying in sid for a long time.