I have just put several of these together and here are a few additional notes for your build and test cycle:
1. When soldering, be careful with C4 and C5, their pins are very close and liable to jumper. I know I'm a soldering newbie, but I managed to jumper three times in four and for the last two I was expecting it and still managed it...
2. There is a small bug in the boards.txt addition in the download:
This:
sanguino.bootloader.path=atmega644
Needs to be replaced with:
sanguino.bootloader.path=atmega644p
(Thanks to Adrian Bowyer documenting that, I saved the final 1/4 of my hair from being torn out.)
3. I have found that uploading from the Arduino software to be a little more pernickety for the Sanguino than Arduino. Using the Arduino software under Windows to upload sketches, I found the most reliable way was to verify/compile separately (thus timing on the next bit is accurate), then hit upload, wait one second and reset the Sanguino.
4. Finally, your debug LED has moved from pin 13 on the Arduino to pin 0 on the Sanguino, don't be too suprised if your Hello World flashing on pin 13 is invisible.
Oh, and I went though all kinds of hell with Vista, my previous devices (Arduinos and anything similar with a USB controller) had used up COM3 to COM10, so the USB->TTL cale mounted at COM11, apparently COM10+ is a problem for the Arduino software, so lots of faffing about was required to get the cable moved from COM11 to COM3 (I ended up deleting my Blackberry driver and associated COM2/COM3 ports to free some up, who knows what will happen the next time I try to back up my phone...)
If anyone knows how to release COM ports reserved for USB devices that are not currently connected, please let me know.
And if anyone knows how to legally downgrade to XP (in the UK), I'll be eternally grateful, I am coming to despise Vista, my WiFi driver randomly believes I am no longer connected to the Internet (Disable then repair connection to fix), and I cannot free up COM ports, I'm tempted to buy something like an Eee, just because it has XP rather Vista preinstalled on it! If I had the time to fight with Linux again I'd consider doing one of my bi-yearly "install a Linux distro and fight with it for a month before giving up" routines.