The biggest change in is undoubtedly the shift towards a full open-world. Long gone are the days of separate [[link]] zones; now we can walk from end to end with no interruptions—besides killing hordes of bandits, of course. However, this change has always made navigation that much more complicated, as we're not restricted by closed-off locales and predictable corridors anymore.
Because of this, Gearbox made the baffling decision to remove the traditional minimap in favour of a compass at the top of the screen. Sure, the compass is useful for getting your bearings, but it's also completely useless in pinpointing enemies in combat. There's a psycho to your northeast, but they could be standing right in front of you or ten blocks away. See what I mean?
Plus, you can use the combat radar alongside the compass to have the best of both worlds. With the radar enabled, enemies will no longer be marked on the compass, making it way less cluttered than it is by default. So, use the radar to track your enemies, and the compass to track your quest objectives and other open-world activities with no messy overlap.
Whether you're a Borderlands veteran or not, try it out and see what I mean immediately—it's a great boost to your situational awareness. Really, the radar should be enabled by default, as most people are [[link]] going to completely gloss over this option and needlessly struggle on with the compass. It's not optional in my eyes.