It's funny, I am the other way, I don't use very many tags except IN calibre (I still frequently use the calibre reader because I love that the down arrow can scroll down line by line - wish one of the readers on the sony - sony's own reader, fb, or cool, could do that).
Yes, I use some collections or tags, but more general in nature. "Fiction, Religious, Canadian...." etc.
It's funny because this was one of the reasons I bought the T1,
I had a Kobo Touch previously, and I used to whine on the feature wishlist thread, "Please put this and this and this in your next firmware, because I see that Sony users have that feature."
Months went by and I thought, heck, if I am wishing for the Kobo to be like the Sony, why don't I just darn well GET the Sony! haha.
I like having a selection of "currently reading" on the homescreen. with the touch of a finger I can get right back to the few I am using.
So at present I have the three "types" of readers installed on it, and don't know how or where if there are more out there to choose from. I'm kind of picky and want to try as much as is available.