Apple confirmed that it's aware of the issues and posted some suggestions on how to fix them:

Symptoms:
Under certain conditions, iPad may not automatically rejoin a known Wi-Fi network after restart or waking from sleep. This can occur with some third-party Wi-Fi routers that are dual-band capable when:

• Using the same network name for each network
• Using different security settings for each network

Resolution:

If you encounter this issue, try the following:

• Create separate Wi-Fi network names to identify each band. This can be done easily by appending one or more characters to the current network name. (Example: Add a G to the 802.11b/g network name and an N to the 802.11n network name.)
• Ensure that both networks use the same security type (WEP, WPA, WPA2, and so on)
• If the issue persists, reset your network settings using Settings > General > Reset > Reset Network Settings.

Note: Always ensure that your Wi-Fi router firmware is up to date.

Sources:
How to Fix the iPad's Wi-Fi Issues - Ipad wifi - Gizmodo
iPad: Does not automatically rejoin known Wi-Fi networks

thank’s for share this info and enlighten Apple care and listen their customer

Sweet, thanks for the post.

does it work?

Yes ... I took my iPad on a biz trip and upon powering it up in the hotel, no wifi at all ... Downtown Philly has tons.

I hard restarted the iPad and wifi came back .... It sucks but it's the price of early adopting

My iPad connected fine to my home router but kept failing with the Sprint Overdrive. I ended up just changing from WEP to WPA2 Personal and have not had any trouble since.

Has this worked for anyone else?

Installed a D-link 615 with wpa! Problems are solved!