Being able to sit in a public without breathing someone else's smoke, undoubtedly a good thing. Having our choices dictated to us by the government, really not a good thing. What is needed (IMO, at least) is finding a middle ground between these positions.
Personally, I don't think the government have been very honest with their intent when it comes to this legislation. They were selling it on the grounds of preventing passive smoking, and yet were talking about exceptions based on food being served? Seems like a mixed message at best.
So, why not a total ban? Comes down to freedom of choice. As an individual you (should) have the right to do as you wish so long as your actions do not impede the freedom of others to do as they wish. I have the right to smoke, I don't have the right to force my smoke on others.
Whilst in modern open-space vertical drinking venues I appreciate smoking sections do nothing to aid a smoke free evening because the non-smoking section is still sharing air with the smokers we could go the way of the traditional pub. Why not provide a smoking room separate and shut off from the main pub and without a service area? That way staff only have minimal exposure when collecting empties and smokers have the freedom of choice which they as individuals should be provided. This is an option touted by many (including CAMRA) and yet completely ignored by the government.
Perhaps they just thought it too hard to enforce, I'm more inclined to believe that they think they know best and that we, the public, are incapable of making our own decisions.
Still, a bit late now, eh? :)