Just thought I would add a couple of post-cruise comments to this thread. We had no problems, and the staff was incredibly tolerant and understanding. In fact, the first day we were too rattled to have remembered to dress up at all. We volunteered to go back to our cabins and change, but the staff insisted on letting us through regardless, providing some ready-made excuses for us: Things like "Maybe your bags were delayed getting to your cabin?" and "It is the first night, no problem".
Very pleasant and we never felt pressured by the staff. Sometimes, we felt a little under-dressed when compared with some of the ladies evening wear. But it was all good. An excellent time.