Image::Delivery is a spun-out CPAN version of an amazing zero-conf O(1) cache for arbitrarily transformed information products that I wrote while doing my code generation system...
It was the culmination of 18 months of intermittent hacking, and after PPI is probably the most sophisticated piece of code I've ever written. I'm intensely proud of both the algorithm and implementation.
One day, I'm going to use it to write the most amazing photo gallery application the world has ever seen! (Once I get some tuits, sigh).
But to be honest, the release to CPAN was mostly a cathartic process for me, since I'd kept it proprietary for a long time, until I realised nobody understood it well enough to pay for it (although it might have ended up in Wikipedia at one point, but that's another story).
I honestly never expected anyone to ever actually USE the CPAN version.
So I'm overjoyed to see someone has actually used it (and likes it!).
I'd call the review completely fair, it IS a little tricky conceptually to understand.
It just goes to show that, especially in areas where there are no really good solutions, you should always release to CPAN, even if you aren't sure anyone will ever use it.