iOS 5 beta 2 has just been released.
This articles just comments a few differences, updates and so on from beta 1, so you should read that article also.
First of all, there is a prettier animated welcome screen, similar to the Mac OS X welcome intro, you see "Welcome" written in all iOS supported language moving along the screen.
When you restore from a backup, the setup assistant does not appear as it did on beta 1 (this is the expected behaviour).
iTunes sync per wifi is now working, or almost.
If you just happen to be intelligent enough to use your desktop wired to prevent famous wireless issues (read: disconnections, interferences, one tenth of cable speed) it will simply not work.
Indeed you may have experienced the same when using any other kind of wifi autodetection (like some third party apps with desktop counterparts use) or even with Apple TV syncing.
This is because all of that is done on Bonjour, a software service that allows auto discovery of devices, but sometimes does not work between wifi and wired networks.
So simplifying the question:
Do you have both iTunes computer and your iDevice running on the same exact wifi network? It will work flawlessly.
Do you have iTunes computer on a wire to the wifi router/access-point your iDevice is using? It will probably not work.
I've been testing for hours just to find my iPhone founds iTunes (using a Bonjour browser) but my computer does not find the iPhone, and, in any case, iPhone says it's unable to find the iTunes library.
There are also a couple of minor bug solved (that I can't talk about), but anyway the system feels almost like finished.
Finally, there is still nothing about iTunes Match, which in any case may not be available outside US until some months past launch.
** EDIT **
After rebooting, retrying, reconnecting, the iPhone appeared magically when I just forgot about it on the Bonjour browser on the iTunes computer, and now it is syncing via wifi.
The screen on the iphone simply says "pass 1 of 4" and on iTunes ("pass 1 of 6", funny) the device appears as if it were connected directly.