Should I Stick to Unlocked Jailbroken 3GS 3.1.2 or upgrade IOS?

[aoreo]

I currently have an ATT iPhone 3GS, 3.1.2, baseband 5.11.07, jailbroken with BlackRa1n and unlocked with sn0w. I've been debating for months now if I should upgrade to 4.2.1 but haven't done it yet. I've been reading some reviews about how people find their phone much slower on 4.x with a 3GS phone. So not sure if I want to do the upgrade. What I have now works for me... although a little annoying some apps need the updated OS. The only thing is from time to time my phone completely freezes and when I try to boot it gets stuck on the apple logo. Then I have to restore my whole phone, jailbreak and unlock again. Not sure if it's something due to the jailbreaking or unlocking. Is there a more stable/app method preferred for jailbreaking and unlocking? I chose BlackRa1n since I found easy steps to get my phone to tether for free (not using MyWi) (that's what I need on my phone the most).

And that was one of the reasons why I was thinking of upgrading... in hope to get rid of my phone freezing from time to time (and for multitasking feature, which I've read really slows the phone down).

If upgrading is a good option, can anyone point me to a good tutorial on how to do this? I've seen some stuff on forums and youtube, (ie using redsn0w and then ultrasn0w thru cydia) but was unsure if I proceed with an upgrade with the current state of my phone? For example, do I upgrade my phone while it is jailbroken and unlocked? And will it be ok that I jailbroke and unlocked using Blackra1n initially?

Any tips to make it smooth will be greatly appreciated!!

[Simon]

You would need to make a custom 4.2.1 with pwnage tool or snowbreeze to restore to so that you can preserve your baseband and still unlock. You can click on the "can I unlock" link in my sig for tutorials on how to use them.