Well, I will apologize for my sanctimonious attitude in my original reply. I will pass it off to the time of night, and the issue at hand. Having lost a friend to a drunk driver, I get more than a little touchy on the subject.
First, to bring it back to the original question, "has anyone mounted a succesful defense to an impaired driving charge" (I am paraphrasing), the answer is obviously "yes." Now, in hindsight, I may have read some of the other responses a little quickly, but what I was reacting to so harshly was I read them as a series of "here's how to beat the charges" messages which got under my skin, as they are obviously related to a very specific set of circumstances. This was my point -- the anecdotal evidence isn't particularly helpful as each case is unique. But, as was so helpfully pointed out to me, the original poster wasn't looking for specific strategy for the case at hand.
Now, on to the two specific issues that came up as rebuttals. First, the time limits. I will not doubt that someone may have been succesful in defending against a DWI due to the length of time between breathalyzer and blood test. That is obviously a factor. My contention was with the absolute nature of the time limit. While two hours may have been the case for you at the time (15 years ago as you point out), the criminal law and jurisprudence has evolved since then, as has the technology for measuring blood alcohol. The particular circumstances would have to be evaluated, but I accept your broader point that time delays are an important factor to consider and evaluate.
As for Maggie Trudeau, again, my point was that she had a particular set of circumstances that allowed her to use a Charter argument, and her positive ruling had a lot to do with the officer having changed his story. I will, however, point out that I am apparently not the only one who believes the case is under appeal:
http://en.wikipedia.org/wiki/Margaret_Trudeau
While the inital article cited indicated that there was no indication that the Crown would appeal, this is quite normal with complex cases (which Charter issues are), and the decision would not be made until some time after.