There is a lot to see and do here - and the queues for the cable car to Mount Floien aren't that bad really. If you enjoy walking it's worth allowing plenty of time at the summit as there are many intersting walks - you could make a day of it by taking a picnic.
The Bryggen is a must see of course and I recommend "Juhl's Silver Gallery" for high quality, affordable (but not cheap) souvenirs.
Norway is an expensive country but if you spend enough in the right shops you can claim the tax back on the ship as Norwegian tax officers attend QM2 (and other ships I presume) to supply tax refunds when the ship is berthed in Bergen.
This is a lovely little village with plenty of good walks straight from the quayside. It also offers the opportunity to get superb shoreside photographs of your ship if she is berthed on the quay. If the sun is shining it is worth paying for the delicious soft ice cream to enjoy whilst you admire the stunning views.