There is a myth saying that having a BAC in the 0.129% - 0.138% range can improve your cognitive abilities. This effect is called the Ballmer Peak (a reference to Steve Ballmer, CEO of Microsoft) and is pictured nicely in this xkcd. Is there any truth in this myth?
This article by Norlander specifically studies the relationship between moderate alcohol consumption (1.0ml/kg body weight) and creativity. According to my very rough calculations, this would correspond to a BAC in the range of 0.12–0.14 for a 73kg human. The paper concludes
In other words, moderate alcohol consumption does improve certain types of creative thinking, while inhibiting other types of creative thinking. Since the skills required for computer programming are solely cognitive in nature (discounting the motor skills required to type, of course), and given that creativity is a large part of computer programming, it is at least plausible that one might gain some amount of improvement from alcohol consumption.
There have also been studies on the relationship between alcohol consumption and creative output. That study examined 34 well known, heavy drinking, 20th century writers, artists, and composers/performers. It concludes:
So for a small portion of people there was a notable increase in creative output as a result of alcohol intake. It does appear that the study did not control for the quantity of alcohol intake, though, so this may not be directly applicable to the Ballmer Peak.
The best study I was able to find on the subject was by Lapp, Collins, and Izzo. They gave subjects vodka tonics of varying strengths (by varying the ratio of tonic to vodka), some of which did not even contain any alcohol. The subjects believed that they were drinking a standard-strength vodka tonic. The subjects then were asked to perform a number of cognitively and creatively challenging tasks. Here is what they conclude:
In other words, alcohol can improve certain aspects of one's cognitive ability, but this effect is not likely due to any pharmacological process (i.e., it is often sufficient to merely believe that one is drinking alcohol in order to achieve the same benefit).
And remember: The Ballmer Peak, as it is currently understood, is but a two dimensional projection of what in reality is a higher dimensional space, vi&.,
New study at the University of Illinois at Chicago reported by Medical daily: Drinking Alcohol May Significantly Enhance Problem Solving Skills
Here is the related scientific publication
—Uncorking the muse: Alcohol intoxication facilitates creative problem solving by Andrew F. Jarosz, , Gregory J.H. Colflesh , Jennifer Wiley
If we think about driving a car, it is generally agreed that there is no alcohol level at which one is a better driver than when one is sober. This document lists some of the findings:
(Alcohol does of course impair judgement, so it is likely that there is an alcohol level at which one believes one is a better driver, even though one isn't.)
Computer programming is a significantly more demanding task than driving a car, and it is extremely unlikely that there is any level of alcohol at which one is really a better programmer than when one is sober.