AZ, I wondered the same thing when I heard about this. I would have to know more about the exact extent of sharia. All we hear about are the scarier bits, but I presume it also contains basic rules about not committing murder, theft, arson, etc. If that is so, then "basing" a system of laws on sharia seems pretty vague, and may be innocuous. But that's just speculation.
So far, if it's just changing policies on usury, polygamy, etc, then it doesn't sound all that bad.