Short write-ups, mostly so I can find them again later.
Throughput on long, slightly lossy paths went up noticeably; on the LAN nothing changed at all. The real win was fewer complaints about slow uploads from far-away offices. Remember to pair it with the fq qdisc and to load the module on boot.
Almost nobody. Old monitoring agents and one ancient load-testing tool were the only casualties. Every current browser and HTTP client handled it without a hitch.
Set SystemMaxUse and MaxRetentionSec explicitly. The defaults are sized for the disk, not for your patience when grepping logs.