hi dbamta!
great question, and also some great insight from those who have posted already.
i'd have to say that one of your biggest challenges/priorities once you get a 6 string should be adopting a technical approach that effectively manages the string muting and string crossing tasks. a lot of players have some technical shortcomings exposed once they switch to the 6... it requires more attention if you want to keep things clean and accurate and also avoid sympathetic vibrations from the strings that aren't being played. i personally deal with this by integrating what i refer to as a 'thumb trailing' or 'movable anchor' approach. this approach is not unique to me, but it is something i discovered early on in my playing career when i first made the switch from 4 to 5. at that time, i realized that the technical approach i was using that was working great for 4 string was allowing a lot of 'sloppiness' to be revealed when i had the 5 string in my hands. i essentially overhauled my entire technical approach, and replaced it with a method that was universal to all basses, regardless of the number of strings.
here is a video i shot for d'addario a while back that demonstrates the basic approach:
Adam Nitti's Moveable Anchor Technique - YouTube
keep in mind that everybody's hands are different, and you may find that you have to slightly modify the approach or fine tune it to better fit your anatomy or playing style. the bottom line, however, is that once you discover how much more efficient you play using this approach, you will never go back.
hope that helps!