Until recently you could only save SHSH of the last IOS was available, regardless of which you had installed, so if you had an old IOS (older than the last) could not save SHSH of the IOS.
Now with the tool you can extract the SHSH iH8sn0w any IOS you have installed, but not the last.
You can also create a custom firmare with SHSH included to restore your own version (not updated).
Changes in version 1.2 are:
- Added support for the iPod Touch 2G
- Fixed issue that created a DFU loop (reboot loop) when using the firmware created.
- Fixed problems with Windows XP
- Source code available soon.
The MAC version will begin to unfold soon.
You have all the info on SHSH here .
Got a tutorial on its use here .