I should have clarified. My 4.2.1 is jailbroken and customized on how I use the phone. I want to go from JB 4.2.1 to a JB 5.0. What's the best way to do that?
In the past I had to "cook" the IOS I was wanting to load to my iphone.
So, I can take my JB 4.2.1 phone and download the apple iOS 5.0, then upgrade via Itunes and not lose the JB Apps or Cydia? I want to make double sure before I go ahead and do so.
Regardless of using custom fw or not you'll always lose jb data. If you're inquiring about backing up that data, look into using pkgbackup or SSH into your device to back up manually. Your apps, if you sync to iTunes you can always sync them back into your iPhone after upgrading.
The easiest method, without needing an unlock, is to just upgrade to stock fw and jb with Redsn0w. Or you could do as you said, create a custom fw for 5.0, set into DFU mode, and restore to it. If you need an unlock then using a custom fw is absolutely necessary, if not, a standard upgrade to stock 5.0 is fine as well.
So I stayed up til the wee hours of the night and decided to upgrade my Iphone 4. I went from JB 4.2.1 to official iOS 5.0. I then ran RedSnow and JB the phone to be a tethered JB.
All works fine for the most part.
One thing that is a little annoying, after my JB, my buttons/apps don't load like they should. I have to swipe a page to the left, then come back and then the app will run. If I don't swipe to another page, the app does nothing when i touch it. Any ideas on what's going on there?