Like others in this forum, I had my issues with iCloud syncing, and I reverted back to iTunes-based syncing.
When Sync over WiFi was first announced, I thought it was great news: I would no longer need a cable to sync my iPhone.
Well, it turns out that the functionality is there, but the "iPhone must be plugged to power" constraint simply voids the "wireless" syncing: you do need a cable, albeit for power, not for communications. Plugging it to power means getting out the same cable needed for syncing over USB.
So, while I can see cases where Sync over WiFi remains useful, it voids it in many cases, such as the common case "my iPhone is not in its dock, and I need to quickly transfer something to/from my iPhone".
Apple, can't you trust us to read the battery gauge and let us take the risk of syncing over WiFi even if we are crazy enough to do it with a 90% full battery ?