lol, 30000 rate.
30000 rate is the most Source supports. Thus, using it means the server will always try to send you as much data as fast as possible. Of course, that's only good if 1) your game/mod somehow needs to send that much data in real time, and it doesn't 2) you have that much download bandwidth, which you probably do 3) the server can hit everyone with 30000 and not run out of upload, which it usually will.
10000 is fine. Higher doesn't help except in special cases. But it doesn't hurt you, unless you are a server host who doesn't set your max client rate appropriately according to your server's connection.
For example, a few nights back one of our spare-box-at-home hosts was having sold 400~700 pings for all clients when a fifth man connected. I told him to set sv_maxrate to 5000, and everyone's ping dropped to 40 and gameplay quality was unaffected. He just doesn't have the upload rate to let Source send the low-priority data all the time.
