I bought my unit from challenger, the mines and my unit is having the same problem too. I wanted to exchange for a new unit, so I should go to challenger itself or apple service centre in times square?

So we shall take our units to the place we bought from or directly go the apple service centre?

As I know, Apple provides 14 days for the customer to exchange their unit 1 to 1 in case like your unit is having manufacturer defects. After 14 days, your unit is no longer applicable for the policy and you will have to send your unit to service centre to diagnose/check before you can claim your warranty ( get new/recon unit). This is what the Switchers told me, correct me if I'm wrong.

Cheers

Go to where you bought your iPad 2 and ask for one to one exchange

Just stay with it if it's acceptable for you because even you ask for exchange now, it would be the same, only slightly better or worse.