I knew there would be something changed that didn't make sense to me
Here goes, the D80 has both a bulb and a time mode.
Bulb = keep shutter open as long as shutter release is depressed - close shutter when released
Time = press shutter release once to open shutter and a second time to close it
Bulb and time can be used with either: Shutter release, infrared remote, or wired remote.
D600 only supports time mode with the infrared remote, not the wired dc2 remote or the shutter release.
Upshot is that you can't use radio triggers to operate time mode, which is a bit of a shame IMO - not the end of the world, but I'd have liked to have that option.