I've heard it is an extremely old ship... (introduced in 1986 maybe?). I think you might want to choose a more up to date ship. But than again, I've never been on it so I'm just telling you what i've heard from others!
We were on the Jubilee about 2 years ago. It was o.k. nothing special. It was clean, rooms were large enough, typical carnival. If you've never been on a cruise before, it will be just fine. Had a great time.
I have been on the Jubilee for our first cruise back in 2002. It was just fine. I've been on Sensation, which is a larger ship, and did not see much difference. The decor and service was the just as great.