The overall reaction to the Apple IOS 4 update has been very positive, even on the older 3G of which there is a review at my friends' blog here. Unfortunately the update doesn't appear to be set to be released for iPad's until later in the year. This is bad for us because the iPad appears to be causing us some wireless problems that won't be fixed until it is update to the latest firmware.
The problem we are having is that the iPad's are keeping their IP addresses after the DHCP lease expires. Then the DHCP server is allocating the (what it thinks are) free IP addresses to other devices that then do not get a network connection.
The problem appears to be with the iPad sleep mode. The iPad will go to sleep with an IP address and will not try to renew its lease. It will wake-up and decide to keep the address it had before, even if it has been assigned to another computer. It does this even if it stays connected to a network when it is in 'sleep'.
At present we need to de-authenticate or disassociate iPad's with access points to get other users to access the network with their devices. There is also a workaround for iPad users here but Apple has promised a fix with IOS 4.