Rendered glass/plastic bottles have fuzzy edges

I'm doing a series of soap bottles and I'm not happy with the crispness of the final images I've been getting.

I need the bottles to be isolated with out groundshadows. so I've turned that off in the scene settings

My image size is 900X 200 px at 600dpi

I've set the materials to be a plastic with an opacity of 15%

1) A PNG output does not give me a transparent backgorund

2) Trying to mask a PSD layer results in pixelated mask outlines.
What am I doing wrong?