Is it? If not, can I update the firmware to optimize it?

Also, if someone would be so kind, could you please tell me exactly what WA is and how it works?

The Digital Rebel does not support write accelleration, a Lexar technology. (WA enabled cameras allow speed increases by up to 23% vs. a standard 40XPro card.) Currently only Kodak, Nikon, Sanyo, Sigma, Pentax and Olympus licensed WA. A 40X CF card would actually reach 8MByte/sec with WA.