This may be old news, but I got a TEAC 540E/KIT yesterday and it showed the buffer size as about 6MB. I read the CDFreaks review that talked about the buffer size. The new firmware version 1.0C fixes the buffer size so it now shows 8mb.
At present I don't have much to burn so I took Comanche 4 off the CD and burned it on to a blank. It took 3 minutes and 4 seconds. Seemed fast to me. Was it?