Not a complaint or request for help - simply some information.
Having downloaded the 'GutenTorrent' collection and added this to my Calibre library, the program is now handling 12,000+ books.
(This is on a E6600 2.4 GHz Core2Duo machine with 2GB ram running under Vista Ultimate 32-bit and Calibre 0.4.83).
1) Most importantly the program works as intended without any apparent tendency to fall over!
2) Startup without connection to the reader takes a little over 4 1/2 minutes from launch to showing the book list.
3) Adding a new ebook to the library (lrf format, normal novel size) takes ~90 seconds.
4) When adding a book the cursor doesn't change to the 'busy/waiting' cursor (Vista's spinning hoop) until 10 - 15 seconds have elapsed.
5) Searches are fast - e.g. only three or four seconds to pick out 35 books with "oz" in the title or author (including 7 "Oz" books)
6) Reordering the display from 'title' sort to 'author' sort took about 75 seconds.
I now have to decide whether too much choice is too much of a good thing, and if so how best to delete most of my library.
The most obvious issue is start-up. The first couple of times I tried this I (probably wrongly) assumed Calibre had crashed. Now I just read a book while waiting...