Faster and easier
I finally picked a new 8G SD card and put the Raspian image on it, I was immediately very impressed, congratulations this is an impressive community effort. This is definitely a vast improvement for new Raspberry Pi users and a no-brainer for most people using one of the Debian Squeeze or Wheezy images. The key performance improvement (among many) is that hardware floating point arithmetic is supported.
Config improvements
There is a small partition that is mounted on /boot when looking at things from the Raspberry Pi console end and is also probably the only things you will see if you put your SD card in a Windows PC. A fair amount of fundamental configuration can be done in here via a optional config.txt, in the past you had to create this file yourself. On the Raspian image a default is already included and if you read the file in a text editor there is a lot of help text and options commented out. It was much easier for me to set up a nice configuration, for example forcing the resolution of the console (the defaults uncommented work great for me) with:
# uncomment to force a console size. By default it will be display's size minus
# overscan.
framebuffer_width=1280
framebuffer_height=720
Without this the default resolution that gets selected with my TV is far too high, teeny, tiny text and unusable unless right up close. I also took the opportunity for the simpler safe overclocking of the arm processor from 700 to 800Mhz.
The sweet spot though is that once you fire up the Raspberry Pi for the first time it takes you through some configuration screens (some of the options in the configuration file plus standard thing like keyboard).
Perception
I have not done any formal performance comparison so can only say that using the desktop feels much faster and slicker. The default Midori web-browser is more pleasant to use and I think a new version (a couple of sites that didn’t work before, seem to work now).
Packages and software
Some packages won’t be available right now but I haven’t had any problems with things that I wanted and also got a bonus in that I could install node.js with apt-get. In theory compiling software from source should work better also as the architecture should configured correctly.