My family and I did the MK cruise in October. It was wonderful. The boat came and picked us up at the GF Marina. Right on time. The captain introduced herself and helped us on board. We set off for a little cruise around the 7 seas lagoon and visited all of the resorts. At each resort she gave us a few tidbits that you do not usually hear. For example - while we were looking at the WL she told us to look at the overall shape of the resort - it looked like a big bear with certain lights being the eyes, etc. That little tour takes about 15 mins and is very relaxing. You wind up in front of the MK about 10 mins before the fireworks begin.
We had ordered a Mickey cake to be on board and it was at this time that the captain passed out linen napkins and china with our slice of the mickey cake on them. We saw many other boats out there as well. Some people had Champagne on their boat - we got pretty close to each other as each boat just has to kinda hover in the area as they do not drop anchor.
Right after the beautiful and magical fireworks - which was a real treat for us seeing them from a different perspective alltogether, she went to take us back to our hotel the long way so that we could run into the Electrical Light Parade that they do on the seven seas lagoon for all of the hotels. That was really neat also - first time seeing it from the water and it really topped off our cruise in a big way.
It was a little chilly out on the water and I was glad I brought my jacket. While we were there it was quite warm during the day - like in the 80's - but it was still pretty chilly out on the water.
I have never done the EPCOT one - but hopefully will one year!