We lost one of our two cats last January. My wife had/is having a really rough time with it, and I actually took it much harder than I had expected I would. It was sudden; he was only six years old, and had started having violent asthma attacks (that looked and sounded exactly like this:
http://www.youtube.com/watch?v=kG5vB...eature=related) so we took him in. Asthma was treatable, but during the check up he noticed an irregular sound in his heart. They kept him over night and were actually going to send him home (with medication), but after that call the vet called an hour later saying that he had thrown a blood clot into his lungs and it wasn't looking good. My wife drove over there and got there literally the second they had started to call me requesting permission to put him down.
Couple lighthearted observations out of thing: we have a second cat, and my wife (and other people, I guess) were worried that she was going to be upset with her "brother" gone. I never had that worry; he was SOOO mean to her (swatting at her, hissing at her if she wanted to sit next to him or with one of use), demanded all of the attention, and ate her food if we weren't there to stop him. She's been perfectly fine, and WAAYYYY more friendly to us.
Also, there was a pretty embarrassing oversight by the vets on the invoice. Invoice was itemized, and the last two were "Euthanasia," then "Cremation" (wife had to go back to work and had no idea what to do with the body), then the total. Directly below that it read: "REMINDER: Annual Appointment February 15." Scooter will NOT be needing that checkup.
I've got to say, we have DEFINITELY slept better since he's been gone. He was annoying as ****. He'd meow at us and paw at our faces when he wanted fed at 5 in the morning, but he'd also knock anything and everything off of shelves, and off our nightstands onto our heads. If we locked him out he'd paw at the door non-stop, and scratch at the carpet.