I love you, man. No, really, I do. This fixed so many problems for me.
I lagged like heck when first connecting to a server before this.
I couldn't connect to more than one server. If I disconnected from a server, I had to restart MC completely before I could log back on to one.
Every time I quit MC, java was still running in the backround taking up RAM, so every few times I started it I had to restart my PC.
Okay I'm having this weird bug where when I have this class file installed I can't connect to some servers. It's really weird. For example I can connect to mcpvp.com, but not paradisepvp.org (Yes I have confirmed that both are up.) It just says that It cannot connect to server... Anyone else having this?
There has been a known issue with 1.3.1 and 1.3.2 when connecting to MP servers. That also includes getting the pings for servers, which could take minutes just for them all to get connection.
When a server was trying to be logged into, the user may have to wait up to 15-30 seconds while the game client was frozen for them to be let in.
The explanation for this was because of minecraft trying to use java files that may not be in every "active" version of java. Without checking if the class existed in their version of java, minecraft attempted to get attributes of the class. Java's reaction was to wait for it's time out of around 15-30 seconds until throwing an error, which minecraft recognized and dealt with properly.
The solution was pretty simple, knowing the problem. Check if the class files exist before attempting anything else. I guess you could consider it a "null check" (the concept, not the actuality). With this change, I use the Class#forName to check if it exists, in which it will throw an error if it doesn't. If caught, the error will let the method know that the class doesn't exist and not to try anything else.
Below is a file to replace in minecraft.jar. This will require the deletion of the META-INF from the jar. If you need further instructions on how to place the file in, look up a tutorial on how to install mods.