I have just bought a Transcend 4GB SDHC Class 6 card for my L1 and can report the following write speeds compared to my Dane-Elec 1GB 133x SD card. The L1 will write 6 RAW+SHQ jpeg's in a sequence before the buffer fills up. Following the procedure suggested here http://fourthirdsphoto.com/vbb/showthread.php?t=5416 I started the stopwatch at the actuation of the first shutter release and stopped it when the camera stopped writing to the card.
Dane-Elec 133x 1GB SD card: 16.2 seconds
Transcend Class6 4GB SDHC card: 15.9 seconds
Given that 1 RAW+1SHQ jpeg is 19.2 MB, this corresponds to 7.4 MB/sec for the Transcend card and 7.3 MB/sec for the Dane-Elec card.
Martin