Beauty lies in the eyes of the beholder. So, beauty is a subjective term. But based on the way Windows 8 was received, I have to admit that the majority of the consumers felt that Windows 7 is better looking than Windows 8.
Has MS traded beauty for speed? In a way, yes. They wanted their new operating system to run on a wide range of systems including less powerful hardware with greater portability. So, it did make sense to make the operating less resource hungry.
Many users have extremely powerful hardware and in these kind of systems, the difference between Windows 8 and Windows 7 in resource usage is very little and can't be felt.
So, the answer to your question, "Did MS trade beauty for speed?" will be no. Those who have super powerful hardware can't feel the little gain in speed. So, if these users happen to think of Windows 7 as beautiful, they are missing out on beauty with no compensation of speed.
What I feel is that they could have implemented it in a better way. They could have made it possible to install Aero while installing Windows. This way, users with less powerful hardware as well as those with powerful hardware could have been served.