Of course it meas something! just like many numerical benchmarks that show a difference in them but you don't notice the difference in real world applications & games unless you have made a big jump, but its all about getting the optimum out of your system because its the sum of all the tweaks that may add up to a noticeable difference where one will see none.
Getting 5.9 on vista tells that you are at the present peak of the vista rating at the time & have noting to worry about at present time depending on application.
I find vista rating to be a nice & quick basic tweaking benchmark,
My raided disks get 5.9 but when i ran unraided it got a lower score & it really was noticeable to the point that i will never run with out raid again accept for the backup drive but a slow HD speed does not make my games run slow once loaded so that would not matter if i did not care for slow access speeds but would if i was doing video/music work.
Low 3D gfx score would not matter if a did not play games but i do.
My mem is the the lowest part of my system atm at 4.5 because auto mem timings are crap on this mobo with this ram, but will be at 5.8 when i tweak the timings like before & a noticeable difference or would you lot not bother tweaking & leave it at 4.5 because the vista score means nothing right!.
Then again non enthusiast would not bother & your also forgetting that the avg pre-built consumer PC when vista came out would not get anywhere near the top end of the vista score & would be more significant not getting near 5.9 on todays top end custom built setup would be a cause for concern.
OP seeing as i can get 5.8 with DDR ram it my be a timing issue.