I just ordered the nexus to replace my captivate that is now having issues. If I am looking at things right, I could take my sim card from the captivate and put it in the nexus. Then I realized that the nexus is capable of H+. If I were to put a sim card for my account that only supports 3g will the nexus only connect on 3g or slower? Or will I need to go visit my local att store and get a new sim card and upgrade to the "4g" plan?
You can't get Hspa+ with an Hspa sim. The good news is that an Hspa+ sim is free and they will be happy to provision one for you. No changes to your plan.
I used my old Hspa sim happily since I got the GN and just had a new one(Hspa+) provisioned last night. No APN changes. So your old sim will work fine you just won't get Hspa+ speeds.
My old sim was from my i4,I had it in an adapter tray for the GN. Since its easier to put a microsim into a regular sim slot, I had them provision a micro sim and put it back in my adapter tray. If I need to swap it into a microsim phone I'll be all set. I'll just take it out of the tray.
They claimed an Hspa+ sim would not work im my iphone4, I am going to try it right now to find out. EDIT: They didn't know what they were talking about the new Hspa+ sim works in my Hspa iphone4! I am curious whether an LTE Sim will work.
On my stock ROM an H seems to indicate Hspa+ and 3G seems to indicate Hspa.