Fellow Twitterer @sxtxixtxcxh (who has far more graphics skills than I could begin to wish for) answered my iconic plea built a perfect png for the Feedly Fluid app. I made it a full-on icns file and replaced my original, crappy Feedly.icns with it (grab it here). There are a few ways to get it into your environment if you have already used the updater.

Method 1 involves downloading the new icon, replacing the one in ~/Library/Application Support/Feedly with the new one and rebuilding the Fluid app (which is described in the original post).

Method 2 involves downloading the new icon, replacing the one ~/Library/Application Support/Feedly with the new one, then opening up the Feedly.app you made with Fluid (right-click, "Show Package Contents"), sifting down to the Resources folder there and replacing the appl.icns with the new icon (you'll need to rename it to appl.icns).

Method 3 involves deleting the ~/Library/Application Support/Feedly directory and also deleting the Fluid app you built and then re-running the Fluid Updater app and - finally - re-building the Fluid app.

Apologies for the process being less than painless. I did not anticipate the change this quickly and wanted to get the new icon into your hands as quickly as possible. I will be making modifications to the Feedly Update app to take this into account and post a 1.1 version soon.