Colin Watson announced at ubuntu-devel-announce that Feisty RC will be delayed due to problems with certain ATA chipsets and problems with the connection status displayed by the network-manager panel applet. New release date hasn't been announced, but it should be a matter of days.

Update (14.04.2007, 11:06 UTC):
I asked Colin Watson if these issues could delay the final release. He replied (and kindly allowed me to quote him), saying it might be the case:

it is possible that this will delay the final release
by a small number of days, but we are making every effort to avoid that
at the moment.

Colin Watson is an Ubuntu Community Council member and Canonical employee.

Also read: Ubuntu Fanboys (...) - I Almost Believed It.