Leon, it depends on whether or not the client values Top Rated. It's supposed to be attractive for freelancers because you get the badge and access to chat support. On the flip side it's supposed to offer clients an easily recognizable measure of a great freelancer. What happens in reality is that clients choose freelancers based on myriad factors - rate, experience, availability, job history, level of expertise, fulfillment of prerequisites, etc. Top Rated may be something some clients value more than others, but it's up to the individual clients to decide what they look for in a freelancer. You may see an uptick in invitations/hires, but it may or may not be related to the Top Rated badge. Too many variables to say for sure.
It probably helps in the open marketplace, but don't believe people when they say you can't find jobs without it. That's not true.
Some of their internal groups require TR to be a part of them.
Other than that, you can do just fine without it. I think losing it is more of a hit on your ego than anything else. But ultimately if you're not in any of their groups where TR is required, losing it is no biggie.