I have a FAT16 card in a 2.1 OS and upgraded to 2.0.7.
The instruction to access the log via web are to be found in the 2.0.6 announcement, but I get an access denied if I try accessing http://x.x.x.x/16234.txt and maybe I’m really out of my mind but I cannot find any way to see the logs with the iPhone app !
Make sure you update your iPhone app because the logging feature in the app is added fairly recently (I think). When you open the app, there should be a ‘logging’ button at the app homepage.
If you type in http://x.x.x.x/16234.txt in a browser and gets a access denied message, that means no log file has been created for that day. You can always check the content of the SD card by inserting it into your computer. In any case, the logging data is supposed to be accessed through the app.