I'm using 1.04. When I said I made it work in 1.0-rc2, I was using 1.23.
You can replicate this error by just selecting the arduino leonardo board in the 1.0 IDE (uncomment its lines from /arduino-1.0/hardware/arduino/boards.txt if you haven't done it already) and try to compile any u8glib sketch (I haven't tried compiling it with other constructors than st7920 over SPI)
/arduino-1.0/libraries/U8glib/utility/u8g_com_arduino_port_d_wr.c: In function ‘u8g_com_arduino_port_d_wr_fn’:
/arduino-1.0/libraries/U8glib/utility/u8g_com_arduino_port_d_wr.c:80:7: error: ‘UCSR0B’ undeclared (first use in this function)
/arduino-1.0/libraries/U8glib/utility/u8g_com_arduino_port_d_wr.c:80:7: note: each undeclared identifier is reported only once for each function it appears in