I hear ya, Podaar. It was the same with us and Watson this year. J and I have never had a Christmas without him, and putting up the tree yesterday was very bittersweet (his urn is about eight feet away from the tree, on top of the shelf we were always yelling at him about getting on). We still have the other two cats, but neither of them have the, uh, "Christmas spirit" that Watson did.
He's been gone three months, but I think the holidays are going to be tough. Thanksgiving was weird, without him being underfoot and/or countersurfing throughout prep. Nobody had to guard the turkey. We ate in piece without him demanding to be fed scraps from the table. He wasn't trying to pull the tinsel out of our hands, or nest in the ornament box. He wasn't there to get pissed that we got an artificial tree (so, no tree basin to drink from). We won't be there to jump/hide in wrapping paper, or to "help" me build a fire. And in a couple of days, we'll have our first snow...his favorite thing in the world was to sit in a window and go nuts for the big, slowly falling flakes. I'm sure we'll cry.
I've seen it put that you can divide people into two categories..."order muppets" (e.g. kermit) and "chaos muppets" (e.g. Animal, Cookie Monster), and I think the same can be said of pets. Even approaching 15, he was a chaos muppet. It;s too quiet, too predictable without that. Even if the other two are quite happy with him gone, we may need to add a little chaos back into the mix soon...