Touch wood, I have not experienced any WiFi issues with my iPad so far – but I know there are a lot of folks who have been reporting problems of this sort. For those who do, Apple has got a Knowledge Base support article on the subject – with a rundown of symptoms and possible fixes for the issues.
Here are the details, straight from the Apple Knowledge Base article, titled iPad: Does not automatically rejoin known Wi-Fi networks
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
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.
If any of you have had iPad WiFi troubles and tried out these or other resolutions, we’d love to hear your experience.