Some orange guns can be quite hard to see the benefit though. Like Moxxi's good and bad touch healing with damage over time effects.
Moxxi's Touches are purple quality. They're quite effective even if you ignore the slight healing-you-when-you-deal-elemental-damage bonus.
Try out the orange gun, and try the white one. A high enough level difference can render the orange one obsolete. (But you can always stick it into Claptrap's 4-slot locker and let another, lower-level character take it out...)