I should have added, remember to turn off "antishake" or "shake reduction" or whatever it is called, as it may produce soft images when mounted on a tripod. Lord knows I forget most of the time.
Exactly why I use a checklist when I'm shooting off a tripod. I forget most of the time too, but my checklist doesn't. That checklist also reminds me to switch to shooting bank B, where the ISO is locked at 200, switch to manual focus, re-check the aperture, set the camera to mirror up, and close the viewfinder shutter before I trip the cable release.
I would not blame the tripod too much, my older Manfrotto is much heavier, and it still vibrates as does the lens from my observation.
Try hanging about a five pound weight from the center of the tripod. It's not a panacea, but it helps.
Re, mirror lock-up, my understanding is very few cameras have it, even the high end Nikons and Canons lack it. But lately I am not sure. What I use is the 2-sec self-timer (Pentax K10), which is almost as good. But it does consume power. So carry a spare battery. Many pros and serious amateurs that shoot other than people or portraiture use mirror lock up as a routine no matter what the settings, especially for landscape work. This was true in the film days as well, and every manufacturer had high end models with mirror lock-up, especially for the 645 medium format cameras. Lots of mirror vibration on those cameras.
Nikon's pro cameras such as the D2 and D3 series all have mirror lockup. Justan's D80 has it too. Use it. Lock up the mirror and then count to five or so before you release the shutter.
Another thing some cameras are prone too, perhaps all, is extraneous light entering the viewfinder and altering your settings when in any auto mode. I place my hand over the viewfinder without touching the camera! It is not a problem for manual mode, however.
Nikon's pro cameras all have a viewfinder shutter you can close when you're shooting off a tripod. The D80 doesn't have a shutter but it probably has a small plastic slide you can slip in to cover the eyepiece. If not, a small piece of gaffer's tape can do the job. The problem with covering the viewfinder with your hand is that you're liable to bump the thing just as the shutter goes off.