We have. We are an egress firewall company and have been testing our product on Graviton2, privately, for some time now. The ARM builds will be GA in a couple of months but so far we've concluded that:

1. These offer an excellent price to performance ratio for an egress firewall like purpose because of low instance pricing and high network throughput.

2. For our stack written in C and Rust, any performance penalty isn't noticeable. It's basically a NAT gateway filtering by hostnames for TLS & SSH outbound.