You can use pasteurized cider with great results. The batch I brewed 4 weeks ago using pasteurized local cider finished at 1.000 and is sitting quite content in secondary containers, quite clear with a nice little layer of sediment at the bottom.
The cyser I started last weekend using cider from the same source is happily chugging along.
Some have said that pasteurized cider produces a less clear result, but I can only speak to how well it fermented.
It's the preservatives you have to avoid. I believe that ascorbic acid is acceptable, but anything with 'sulfate' in it will kill your yeast.
