I ordered liquid bar snake for my '05, but after looking inside the handlebar I decided to save it for another bike. There's only room enough in each bar to put in perhaps 5-6 ounces of material, at most. IMO, that wasn't enough to bother with, and I'm a stickler for killing bar vibes. If you have yet to install some form of cruise control, do so at your next opportunity. I noticed right away that being able to relax my grip and move my arms/hands around made a HUGE difference. Pick the cruise control you like best, it will really help. I also added bigger bar end weights, which made a noticeable difference.
Some have also said that installing bar risers moved their riding position so that less weight was on the hands, resulting in less numbness in the hands. If you have shorter arms, this would help too. I have long arms, so I passed on this one.