It's funny, the old saying "The more you know, the more you find that you really don't know" really does hold true. I just recently joined a band playing Hard Rock music and I'm actually learning stuff. For the last 3 years I've been playing in Blues, Funk, Jazz, Country, ect. bands. That allowed me to play very busy and take a very upfront role in the music. I then found myself in a band doing more Rock oriented music. (both Classic Rock and Modern Rock) I knew that it was going to mean a lot of root notes and taking a back seat more often than not. Still, I learned something about playing Rock music; while it might not be the most harmonically or melodically challenging music for a bassist, you have to have perfect timing. Since Rock and Metal is a very structured style of music, being all around tight is a must. I'm a little ashamed but humbled to say that Bad Religion by Godsmack kicked my ass the first few times I tried to play it. (yeah, the song with all the D power chords for a verse) Anyways, I guess my point is, there's something to learn from every style of music.