There are plenty of reasons to not introduce a PVC liner into your bathroom - being hard to recycle and offgassing of unhealthy plasticizers among them.
We've used white nylon hotel-style curtains as liners (Restoration Hardware, $20) as a healthy alternative for years with no problems.
They are looooong-lasting, mildew restistant and super easy to keep clean and fresh - we simply throw them in the wash every so often and then rehang in place to let them dry.
Here are a few more AT Links that might be of interest:
Anyone have more suggestions/sources to share?