Appalled that this is Beta 5 as Wi-Fi sync sucks.
This is how it went for me.
Attempt 1: Sent two songs over, iTunes showed it syncing and so did my device. Go to music app, only one song present and would not play.
iTunes stated the songs were on the device.
Attempt 2: Load one song onto device. Song worked but No Album Art transferred (Yes the track did contain it and it works syncing via cable).
Attempt 3: Added another song, in the process it deleted the other song. Yet iTunes still states both are on there yet the device shows one (Still no album art).
Attempt 4: Add one more song, sync failed as device supposedly disconnected when it did not. iTunes shows 2 songs on device now, yet the device itself shows no songs present.
Attempt 5: iTunes can't find device/Device can't find iTunes yet both we're working (Although horribly) two minutes ago. I give up.
So I'm gonna be using the cable from here on out. It's outrageous as this was worse in Beta 4 so I guess it'll go to the GM aswell. This is one feature I hate.