Jeremy, I've done the 120 studies off and on for the last couple years, as it was suggested as good beginner studies along with Diatonic minor and major scales by Segovia.I pulled Gulliani arpeggios out again and have started doing them again.Some are definitely easier than others. I do find my left hand fingers get sore playing the C and Dmin chords for so long, and I have had it suggested by others to just do the patterns without using chords, though this becomes very monotonous and boring.
When doing them, I try to work on different things, sometimes really concentrating on finger placement when strinking the strings, good tone, varied tone voices, speed, hand and finger position, etc. These are really good when you set goals, I think.
By the way, Tarrega has some nice arpeggio studies as well, which some may wish to look into.