yeap u answered ur own question 
i think u should also know why the longer the focal length, the
more prone to shake, at a given shutter speed.
the rule-of-thumb is that u shouldn't go slower than 1/focal
length. meaning, if you're on 200mm, u should shoot at or faster
than 1/200. but dun forget, with digital, there's a 1.5 crop
factor, so at 200mm u should really be shooting at 1/300 shutter,
which is pretty fast and not always practical.
there's where VR comes in. it is SUPPOSED to improve your shutter
by at least 2 stops. so where u shake at say 1/125, u'd be able to
go down to 1/30. it's hard to believe, but it works somewhat.
anyway the reason for this lens purchase is more of the sharpness
at 2.8 than the VR. but the VR (vibration reduction) is extremely
helpful for smokers like me, who aren't very steady at the long
end. just try to remember ur m16 firing days, breathing techniques,
elbows tucked in etc.. same applies for long lens photography.. and
anyway this isn't even considered long yet.. 
or.. use a damn monopod/tripod. 
dun forget that camera shake isn't the only thing that u worree
about when u have slow shutters. u also have to worree about
whether u wanna record movement in your SUBJECT. so what if u can
shoot at 1/4 at 500mm without shaking at all? the
bird/person/flower-in-the-breeze will be totally blur if it moves
within that time frame, which is highly likely.
