Packet loss is extremely low, which is easy to tell using a builtin netgraph.
Screen buffering should be reduced as much as possible and vsync is not something competitive players would ever want. Pros all disabled it in Quake Live for sure.
Players on modern connections that are playing on servers in their city do not need CSP.
In practice it's not that bad to have CSP if it's not really doing much (due to all players being low latency) but I know from playing NetQuake vs Quake Live with low latency that it's nicer not to have it at all.