Yes, lots of people have started using Rust for hobby projects [0] and their feedback has been invaluable to the development of the language.
How much involvement did he have on the project?
(The "mozilla" people (brson and pcwalton) are the people to listen to there.)
Brendan's resignation as CEO will have no effect on Rust or Servo.
Many people at all levels of the organization are huge supporters of Rust, Servo, and Mozilla Research in general.