This was our first, but hopefully not our only, cruise so we have nothing to compare against.
As first-timers I will say one thing firstly: the instructions given each day were a great help and all the things I worry about (not knowing where to go or what to do) turned out to be nothing to worry about at all. Your hands are well and truly held to ensure you know where you need to be and when.
Embarkation was very quick (20 minutes from drop-off outside Newcastle Passenger Terminal to being in our cabin). The cabin was 4119 and was more than adequate for our needs.
The room was perfectly suitable for our needs. Large enough to store everything we had, I'm 6'8" and didn't feel cramped.
Equally the shower was a good size (again I'm 6'8" so that really says something if I think it was fine!).
The only fault would be the TV was tiny and the quality terrible so taking a break in the cabin to watch a movie wasn't worth the time.
Embarkation and disembarkation took minutes. Very easy. We had to take a shuttle the 100m from the terminal to the ship but on our return we found we were allowed to walk it (which made things even quicker!)
You have to take a shuttle from the ship to the port entrance as it is a very busy working port (containers being moved about constantly). The town itself was pretty, easy to reach on foot and so peaceful.
The port was 5kms from the city centre. A shuttle bus was laid on by the port authorities (2000 kroner for a return ticket). It was incredibly busy in the visitor centre and we missed one bus waiting to buy a ticket. They are very infrequent. The second day we decided to just walk it, that's how poor the shuttle bus service is. However, I'd recommend a taxi!
The touristy stuff in Reykjavik can easily be seen in half a day. I'd recommend the city pass as the museums are not free so get whatever discounts you can!
I didn't take an excursion but I think to enjoy your stop here you should!!
We walked out of the port (shuttle bus to town centre was laid on however really not needed). Lerwick isn't the prettiest place and again... we should've gone on an excursion!
The museum is amazing however!