Koreader has also implemented OPDS support, and includes a "Local calibre catalog" selection. I have downloaded books from the Gutenberg catalog, and the ManyBooks catalog, and the Internet Archive catalog. I also added the Baen Free catalog, and downloaded a book from there. Don't forget to poke the WiFi symbol in the top menu to turn WiFi on and off.
Calibre "connect/share" option includes "Start the content server" which will give you the IP address and port data to setup the Local calibre catalog in KOreader. Just tried it and it works fine.
Luck;
Ken
You can give Koreader a try, it will not effect the stock Kobo software.
This is the easiest way I know to install a launcher and the KOreader folder/program. You can download the official release of KOreader
here. There are Kindle and Kobo and Android releases, pick the one for your device.