Episodes 2-4 perhaps don't quite live up to episode one, but they're still very enjoyable, and the other two stories in the box are awesome.
This is what I always assumed and it's not a story that I revisit often as a result of that, but last week I rewatched it again and I enjoyed it a whole lot more. I think it feels a bit disjointed and tacked on to the first episode, but as a story on it's own with the cavemen I actually quite enjoyed it this time around.