First the good news!

WinAVR release 2007/12/21 includes the latest avrdude (5.5) which now supports USBtinyISP! This means you dont have to patch any code or replace binaries to use the USBtinyISP programmer.

However, there is some bad news…

WinAVR was compiled with a 2 year old version of libusb (v0.1.10) instead of the most recent version (v0.1.12), which means that it is incompatible with the original driver that I posted up on the USBtinyISP download page. Thus if you want to use the latest WinAVR, you must uninstall the driver and then reinstall the older (v0.1.10) version which is now available on the download page.
Otherwise, youll get a nasty surprise:

as the device seems to be working, but avrdude can’t “find” it!

If you don’t want to reinstall the driver, you’ll have to replace the avrdude.exe and libusb0.dll with the modified versions (also available and described in detail on the download page).

The other bad news is that I made some mistakes in the code that make it incompatible with 64-bit. Hopefully I will get that tested/fixed for the next revision…not having a 64 bit machine makes it a bit annoying to debug!