Hopefully F.lux works still. That was the worst thing about using a new, unjailbroken iPhone and iPad. Especially now that iOS 7 has a lot of white UI.
It may be an issue with MobileSubstrate, as Saurik just pointed out that the evasi0n team gave him no lead on the jailbreak.
Removing F.lux didn't do anything so I thought it was Mobile Substrate, but removing that didn't do anything until I rebooted the device so I can't be sure.
Other apps depending on Mobile Substrate work OK so far, so don't let it turn you off trying things out.
Are you using an A7 device? I've heard those are the devices that are having the most trouble due to incompatibilities.