Upgrading to 5.0 from 4.2.1 on iphone4 if using Gophone? Safe?

[conqst99]

Hi All,
With the release of IOS 5.0 yesterday, I'd like to give it a go but don't wanna mess up my phone if I can't go back. I currently have the 4 running 4.2.1 and BB 02.10.04. I have it running on the gophone pay as you go plan which works great for me since I mainly text and can get away with about $8 a month for 200 texts. I rarely use for calls. Since its under AT&T (I cut down my original SIM to a micro), I don't need an unlock obviously. My question is if I install 5.0, is there any drawbacks to not being able to continue on the gophone plan (did Apple work something into 5 that will prevent it from running)? The new features of 5 look very cool. I don't need to JB to a tethered version right now, I can wait till the untethered is released but just need to have my phone continue working as before. Do I need to backup my SHSH blobs on saurik's server using Tiny Umbrella and/or Cydia in case I wanna go back to 4 2.1 or can't I (will restoring back in Itunes allow this if blobs are sent to look on saurik server)? I recall reading about Apple stopping the signing or something a few weeks ago? Appreciate any comments / info. Thanks.
Dave

[Simon]

Not sure how updating will affect you being able to use the phone with the gophone plan. I wan't aware you could do that anyway, I though ATT can tell if you are using a iPhone and force you to go into a plan.