If you're not a fan of iOS 8, you want your jailbreak back, or you just made the upgrade on your 4S and it's not working so well, you can still downgrade for a short amount of time. iDownloadBlog shows you how to do it.
The process is pretty much the same as manually installing iOS 8, except you'll download the iOS 7.1.2 firmware instead. You'll need to do this right now if you want to downgrade, because Apple will stop signing iOS 7.1.2 pretty soon. Head over to iDownloadBlog for the full instructions.
How to Downgrade iOS 8 to iOS 7.1.2 [iDownloadBlog]