The patch applied in NET-465 causes a very slow data transfer rate. The line
sets the buffer size to 1024 by default. With this size I had a very bad transfer rate on windows 7 and XP. The wireshark log shows that each FTP-DATA packet is exactly 1024 bytes long and has to be acknowledged on the TCP layer before the next one is sent. I don't know why, but when I set the buffer size to 0 (FTPClient.setBufferSize) the transfer rate is fine.