I just want to say thanks to Marc for sharing this. I know how difficult it is to be objective in a post-mortem analysis, and I think your post is a very balanced (and dignified) assessment.
There's one more important differentiator, however, that hasn't been discussed yet and which pre-empts a lot of this commentary, that I thought I'd share: Mint intentionally targeted a different market.
Most consumer spending in the US is managed by middle aged men and women that are not especially financially nor technically savvy. It was our view that previous personal finance solutions (Quicken, MS Money, and the following web-based solutions) catered more towards the technically/financially proficient, and had therefore missed the larger market opportunity.
So we tried our best to ignore the Silicon Valley drivel around "viral distribution" and "cloud security" and focus instead on issues like "How can we make it easier for a soccer Mom in Kansas to set and meet her monthly grocery budget?".
The Mint brand (including the name, visuals, and user experience) were all designed with this in Mind. They were definitely supportive, as Marc correctly points out, but in no way were they determinate.
I think Mint and Wesabe were both strong products that served their users' needs well. We just happened to target different users, and ultimately there were more of ours.