While an app can't go faster than 9600, if that is the set baud rate, it can go slower.Apps that have a lot of CPU or I/O overhead formatting output can be improved with buffered serial output.
Not much point in buffered output if there is no flow control to keep it from going out once written to the UART.
The 1.0 beta Serial works and is non-blocking as long as no more than 64 bytes are queued.
The buffer helps with programs which send a byte occasionally and need to return instantly. For programs which are sending large amounts of data it makes virtually no difference.
It is a big problem for some apps. If you log fast serial data to an SD, having a large input buffer can improve performance due to write latency for the SD. It avoids dropped data.Now you are required to have a large useless output buffer when you increase the input buffer size.I don't believe the LCD example without more info.