Idea for Software Update
This is probably an old idea, but I haven't seen it around recently (or at all in my case). Spotlight may not be the key to world peace, but at least Apple provides a way to get your special file format indexed. Wouldn't it be nice if Software Update allowed a way for developers to register their app so that users could be notified through a unified interface? Yes, I know there are apps from various mac update sites that do something very similar to this. This would be much simpler for the user, even if it does put a little more load onto the developer.
I guess it would be similar to how Windows Update knows about a few of the non-Windows components on your system (video, nic drivers, etc) only better.