well it depends where you stand in your purchase date. i bought the iPad 3, 32GB LTE-Verzon on October 3 and fall within Apple's unofficial 30 day exchange window. upgrading to the iPad 4 has some hidden costs in my situation though:
1) i would like 2 extra Lightening cables - 1 for the car and 1 for work which = $40 extra (there are no knockoff cables in the near future coming out). i could get by with just the included Lightening cable but that would involve yet another item to remember to put in my briefcase in the morning. currently i have 30 pin cables in both locations. however now that i think about it, since the iPad battery lasts nearly all day i could probably get away with just 1. hmmm
2) i bought my iPad on a business trip in Delaware tax free. PA sales tax will add $44 if i returned my iPad 3 and bought the iPad 4 at an Apple Store in Pennsylvania. to drive down to Delaware will cost me ~$20 in gas/tolls and 2 hrs of my time
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it's a tough call