Great blog post! My experiences with the Sigma, 35 IS and 35L are similar to yours. Admittedly, I only rented the Sigma for a week, but the spotty AF was enough to deter me, regardless of how sharp my in-focus images were.
I absolutely enjoyed the 35 IS for traveling, and it was also in my bag for events. When comparing images between the two lenses, I found that the 35 IS seemed to resolve more detail to my eyes, but I like the overall rendering of the 35L - the colors, the focus fall off, bokeh, etc. I didn't have the budget to keep both lenses, so in the end I sacrificed the portability and IS of the newer 35 f2 for the older 35L.
“Be kinder than necessary, for everyone you meet is fighting some kind of battle.”