Unfortunately, starting with iOS 5, Apple modified the restore system of our iDevices so that SHSHs become useless for the time being for users. Practically no person can restore to iOS 5 even with a saved SHSH, but this limitation could be temporary if the Dev Team could discover a method to exploit the restore system designed by Apple. SHSHs are useless now, but in the future they might become useful again, so I recommend that you save at least one SHSH for iOS 5.0.1 because you never know when you will need it.
The iSHSHit application is the best way to do this. You can find it in Cydia in the BigBoss repo, it is as of today compatible with iOS 5.0.1 and the SHSHs saved with it can be sent to you by e-mail to save them on your computer. I don't know when or if the Dev Team will discover a method to restore to iOS 5, but if such a method is available I will let you know. iOS 5.0.2 may be released soon to solve the problems that many iDevice owners are complaining about, so a SHSH saved now could prove to be extremely useful.
