As the owner of a 1Gbps internet connection and having experienced speeds of 120/200/600Mbps, I have to say that this router is very good up to 500~600Mbps with a "heavy" configuration, along with applied best practices. In my case, with 200 Marking, 20 RAW, 150 Filter, and 60 NAT rules, it still performs above 500Mbps.

For a simpler configuration, it works fine even with speeds above 1Gbps.