For those using TinyISP with ATTinyx4 etc (specifically i use 84A_PU) and TinyDebugSerial at <=8Mhz
I found that on a new vanilla install (for windows 7 64) of Arduino IDE 1.0.3 (downloaded today 8/feb/2013) you should change the
define for the debug register and bit (see 2 lines below 'Use MISO as TX').
#elif defined( __AVR_ATtinyX4__ )
#if F_CPU <= 8000000L
// port B bit 0 (PB0)
//#define TINY_DEBUG_SERIAL_REGISTER 0x18 <<<<original settings
//#define TINY_DEBUG_SERIAL_BIT 0 <<<original settings
//use MISO as TX back to host, i.e Port A 5 (PA5)
#define TINY_DEBUG_SERIAL_REGISTER 0x1B
#define TINY_DEBUG_SERIAL_BIT 5
#else
// port A bit 0 (PA0)
#define TINY_DEBUG_SERIAL_REGISTER 0x1B
#define TINY_DEBUG_SERIAL_BIT 0
#endif
I am very new to all this (1 week in) so I hope the above is helpful, please reply if this info is erroneous and I'll correct.
PS: Thx very much for TinyISP, makes using 84/85's almost pleasurable

Kind Regards