We finally bought a digital camera awhile back and on this last cruise we also brought our 35MM camera, but only used the digital camera, so yes, I think you will use it a lot and they are very easy to use, just takes some getting used to.
Well, we currently have a digital camera, but the digital video camera has the digital camera function built in so we wouldn't have to take the camera along at least - just replacing one piece of electronic equipment with another...
My suggestion is: Take the digital camera you currently own on your first cruise. When you return, take the money you were gonna spend on the video camera and put it towards another cruise. You'll be glad you did!
They're running a really great deal right now (no interest, payments for a year) and they're really cheap (orig $500 selling for $249) since all the new models are getting ready to come in next month...so it's hard to pass up.
But, I see your point - what'll happen is I'll get hooked on cruising and nothing else will seem as important anymore :o)