For the past couple of days, I've been trying out a new book reader on my Android phone called Laputa Book Reader. Here is a link to the AppBrain page describing it.
http://www.appbrain.com/app/com.reader.books.laputa.ui
I haven't completely decided to switch to this yet, but it shows promise. There is more attention on the reading experience (font, background, page animations, etc.) than any of the other Android readers, and it has access to a large variety of online repositories. It will allow you to set up a custom catalog using your calibre content server's IP address and port number (It doesn't support OPDS, so don't include the "/stanza"). On the negative side, it requires you to perform a clunky import of the books you download from calibre and it hasn't pulled down the covers for the epubs that I've imported so far, but I'm still trying to figure it out.
I guess for me now, it just depends on which of these developers integrate the features I want first. For Laputa, I want to be able to open my Calibre content server (with OPDS) within the program and download my epubs (and covers) directly to a location that shows up on the ui's bookshelf.
For Aldiko, I want more reading customization options. I wish I could just combine the 2 into one really good solution.