unlocked ios 4.21 on tmobile, should i upgrade to ios5?

[threetimesdaily]

Hi, I've been trying to figure out if I can jailbreak/unlock untethered a 3gs on ios5?

I've got an iphone 3gs on bband 6.15 running ios 4.21
Should/can I upgrade?
The dev teams blog says I can but then when reading further it seems like i shouldn't?
Has anyone run into any problems doing this? if not how did you go about it?

 

[eastercat]

It's a tethered JB on iOS 5.