Few days back i got my hands on the IOS4 Gold edition which is almost the one that will get released next month. I was in no mood to spend 99$ to try it before release so got the files from internet.
http://download.imodzone.net/ gives you all the files. Basically download iTune beta and the IOS4 relative to what ever device you are using.
JB was also fun and very easy with Red Snow and for that you also need the IPSW of beta 4.
Anyways below is a slideshow compiled for all my friends who asked for. Also i should mention one thing. IOS4 is damn faster than the IOS3 and you can feel it.