Here's another interesting read I've found. --> http://muttaqun.com/niqab.html The hadeeth brother ahmad12 is referring to is in the link as well. Hadith - Bukhari 6:282 'Aisha used to say: "When (the Verse): 'They should draw their veils over their necks and bosoms,' was revealed, (the ladies) cut their waist sheets at the edges and covered their faces with the cut pieces."
The Arabic makes no mention of 'faces' at all. In my opinion, a good place to start such an investigation is the following verse: And tell the believing women to lower their gaze and be modest, and to display of their adornment only that which is apparent [...] 24:31 What is the meaning of 'which is apparent'? I believe there was a difference of opinion between the sahaba and within the tabi'een as well. Some held the opinion that this refers to the outer garments and one eye to see, whilst others considered it to mean the hands and face. I can't remember exactly, but I think Ibn Kathir was of the former opinion and Al Qurtubi and some other commentators were of the latter. Yusuf Qaradawi (not sure what people's opinion of him is) was also of the opinion that this verse was referring to the hands and face. It comes down to what you find more compelling.