I don't know wheter I will upgrade to ios 7 on my old iphone 4. My ipad 1 has become almost unusable on ios 5 and I don't what the same thing to happen to my phone. What are your thoughts on this?
I dont see why not. Unless you REALLY REALLY hate iOS 7 then yeah...
Save your SHSH blobs for 6.1.3, and if 7.0 is slow or buggy, roll back to 6.1.3.
As in do a manual backup to itunes?
Don't worry about blobs - unless you are a jailbreaker.