Yeah, I used Senuti
I ran into 2 problems.
1) Youll probably have to turn off the setting on your iTunes that makes it start up when you connect an ipod. I had to because if i didnt then Senuti wouldnt recognise the music.
2) When I did it the first time the music copied over twice. Once to my music folder, then when i put the songs in my iTunes, for some reason it copied the songs again when it put them into the itunes folder. IE double the harddrive space taken. Easy fix, you just make sure that you configure Senuti to copy them to your itunes folder and not your general music folder. This is all in the help part of the program, they go into depth.