I love all the skill trees so much it's really hard to decide what to spec into and what not to. More skill points opens up even more possibilities and expands on potential playstyles. Which is awesome.
As an Axton player, I dipped into all three trees so by Level 44 I or so I could get Rockets/Longbow/Shields/Mag Lock. Losing out on the end-tier skills, but this combination is an absolute blast to play with.