I liked Dr Boyce. John Hoyt was good in that role and he seemed to be really more than just the doctor, he was in on decision making and seemed to represent at least part of the science division as well.
I heard that they didn't want #1 because Majel wasn't a good enough actress, I didn't think she was so bad, but she and Pike were somewhat flat and even to the point of someone interpreting them as bland. I didn't see it that way myself, but the dynamic that Hoyt or Nimoy had when they had their lines is missing with them. Now, if you're playing a flat emotionless character, that's fine, but it can confuse people that don't realize it's supposed to be that way and think it's just bad acting. But that's a serious drag on a show if two of the leads seem to be sub par.
Most of the other characters didn't get enough to really say too much, but I liked Tyler and Colt, and the other bridge and landing party people seemed competent. That is an important point, I think, though, even though they are background characters/extras if they appear foolish or not believable it doesn't matter how good your leads are, the whole setting is damaged, and setting is extremely important to science fiction.
There are other things, art direction, set design, effects work, these are all independent of the actors but are still important, I thought they were all good for The Cage.