I have made a AVR910 programmer (hw) by Klaus Leidinger http://www.klaus-leidinger.de/mp/Mikrocontroller/AVR-Prog/AVR-Programmer.html
I have tested it with Avr-OspII, Avrdude and Avrprog.
Baudrate is 115200.
With Avr-OspII writting 8 kB into M8-flash takes 9 seconds.
The same with Avrdude.
But Avrprog from Studio does it in 4 seconds.
Why this remarkable difference?