I did the Peppermint Bay cruise and I enjoyed it a lot. It was one of my most favorite activities in Hobart. I recommend a window seat on the catamaran, if you can manage.
However, I didn't like the Salamanca Market too much. I bought all my trinkets here. Later, I saw many of the same items in Melbourne's Queen Victoria market for much cheaper.
I wanted to take the Cadbury Chocolate Factory tour, but there was a strike while I was there. I was also told by others that one should book well in advance for tickets.
Mount Wellington was very, very cold at the top. I knew there would be ice and maybe a little snow, but I was still shocked at the amount of wind and snow at the top.
Good luck!