Yeah, I just use calibre to manage my library. The T1 might want to install the Reader software on your PC when you connect it, but I don't remember if it does or not. I would think you could skip it, if you prefer.
And yes, it has a micro-SD card slot. I use it exclusively for my books and don't store any in internal memory. Unfortunately, I've encountered a couple of minor bugs when using an SD card:
1. You can create a bookmark by tapping the upper-right corner of the screen. The firmware is supposed to add the book mark to your Notes list so you can navigate to the bookmark. This feature works correctly with books stored on internal memory, but not on an SD card. I can create a bookmark, but I can't navigate to it.
2. You can create a new Collection for books using a menu on the T1. If you create one on an SD card for books that are stored there, they are not properly added to the Collection, making it useless. This feature works correctly with books located on internal memory.
These are the only issues with the firmware that I'm aware of, but it wouldn't surprise me if there were other bugs when dealing with an SD card. They're annoying, but I work around them. I generally let calibre set up all my Collections anyway--I just wanted to set up a new Collection that lists books I'm currently reading, since I have a few going at once. The bookmark bug bothers me a little more, but I mainly just use it to mark the place where I left off reading in case the device loses my place, which so far it's only done when I upgraded the firmware with the book I had last opened.
I'd like it if all bugs relating to SD cards would get fixed. I intend to report these issues to Sony support, and hope that others who have experienced them do the same.