I don't like bladders in the winter as it is difficult to keep the hose clear.

I do like a wide mouthed bottle as it is easier to get water in/out if there is a bit of ice in the bottle. You can also keep it stored upside down so that the ice formes on the bottom.

I am going to look at this bottle from MEC to see if it could also be used to heat the water.

http://www.mec.ca/Products/product_detail.jsp?PRODUCT%3C%3Eprd_id=845524442621456&FOLDER%3C%3Efolder_id=2534374302696609&bmUID=1193702880092