There has been a lot of media attention recently about BPA (Bisphenol-A compounds) in baby bottles. Apparantely when the milk is heated in a normal baby bottle, the chemicals leach out of the plastic and go into the bottle. I'm not going to spout on about the research and risks here.
Another option is the Adiri Natural Nurser - which is also free of BPA. Now this is a BEAUTY of a baby bottle. The top quarter of the bottle is soft and squishy like a boob. The teat and bottle are all one piece, and the milk squirts out with the same action as breastfeeding. So with the Adiri bottle, there is less chance of baby rejecting your boob if you are doing a mix of breast feeding and bottle feeding.
The Adiri bottle is great also if baby has been rejecting other types of bottles and teats.