IMO, it depends because the cause of the higher premiums is higher risk and claims because of pre-existing conditions, etc. If they price it right it could be good, but the transparency of the exchanges should put pressure on pricing so the end result will largely depend on whether some companies decide to price really competitively in order to gain market share.
I think there is a reasonable possibility that the exchanges could become a war zone and the insurers will beat the stuffing out of each other price-wise, which would be bad for the insurers.
i can guarantee you it will not be priced right according to anyone. if your poor enough to get govt subsidy thats one thing.