I ran dual CRTs at one point, but when I upgraded and went back to a tower I lost a lot of desk space. When I had my little Shuttle box I would keep one CRT sitting on it as my secondary. My CRTs also started dying and now the only working screen I have is my LCD.
And yea, it was annoying that I had to disable the second monitor for some games. Though I really mostly used the second monitor like it was a second PC, with a web browser or media player on it while I had a game (herm, WoW) on the main one.