Originally Posted by aidanz
no you don't need SHSH blobs.
if you are updating to an official firmware then you just need to Shift-Update the iphone.
i updated an iphone from 3.0 to 4.0.1 (instead of 4.0.2) the other day using this method.
i think what karma_ was trying to say was if you intend to upgrade, it is recommended that you do a shsh backup.. Also does not matter what version iOS you have. you should still do a backup of shsh for all newer versions available. meaning newer than your one! So in a nutshell, you can not upgrade to any version inbetween without signed shsh blobs!!
heres an example why:
if you have 3.1.3, you should backup 3.1.3 & in this point in time apple is signing 4.3. so this means you are ONLY able to backup 3.1.3 & 4.3...
even though you might not use 4.3
now imagine in a weeks time from now 4.3.1 comes out... well this means you can now backup shsh of 4.3.1 too. which would mean you now have 3.1.3, 4.3 and 4.3.1 backed up.. hope that made sense