In Australia we have a 0.05 limit on BAC plus a 0 limit on provisional (usually under 21) drivers. 0.08 is the point where you are obviously going to fail at driving. 0.05 is where you think you can do it but more likely than not cannot.
After seeing how friends dealt with the 0 limit on provisional drivers and in light of the fact I don't drive myself, I'd support a 0 limit - it encourages a lot of caution and forethought, particularly the morning after when you can still be drunk and might think it's just a hangover.
I don't disagree with the sentiment that people who are intoxicated should get the fuck off the road. There are other distractions drivers have to worry about, but drinking and driving is unnecessarily lowering your awareness, negatively impacting your response time and making your large heavy vehicle a hazard to everyone else.
At the same time, a 0 limit means you'd pretty much have to avoid all substances with trace amounts of alcohol, which would be difficult from a practical standpoint. Start looking at how many brands of mouthwash and similar products contain alcohol, and you'll see what I mean.