I can't be the only person who downloaded mp3s from Limewire and uploaded to my iPod. I think a lot of my friends did that too. Were the majority of iPod users already locked in by that point through the iTunes ecosystem? If so, what locked them in (the song purchases)?
I always used my iPod Nano with KDE's music player/library AmaroK. I also had a Mac at that time, and purchased a lot of albums too. Since DRM was removed at that time, I either added them to my music library or copied to my iPod via my Mac.
At the end of the day, using an iPod and iTunes neither limiting nor locking-in.