The October issue of Linux Identity, a "Duo Pack" with Ubuntu 10.10, included a review of Tellico and GCstar. It's a French magazine, but through the power of the Interwebs, I ordered a copy and received it in the mail recently.
It's always interesting to me to read what specific features or workflows each review mentions. This particular review gave step by step instructions for installing and running Tellico on Kubuntu, and then basic steps for adding information about a book to Tellico. It also included information for creating a custom collection (which I don't usually think about most users doing) and using a filter for finding items in a collection.
It didn't appear to have any comments about drawbacks or bugs (other than a quick aside about needing to register for an Amazon API key). The article includes a nearly identical review of GCstar, basically walking through installation, running, and adding a book.
One note of interest to me, as well, was in comparing the screenshots between Tellico and GCstar and looking at the translations of the user interface in French. I guess it doesn't always register to me that there are so many ways of saying the same thing, especially in English and no different in French. Slightly different verb tenses or phrasing...