It really won't make much difference if the reason for those holding out is they don't have the hardware to have already upgraded to Vista, they would have the same problem with Windows 7 as the spec is effectively the same as Vista. MS have said that those on Vista will be able to run Windows 7 on the same hardware without a need to upgrade it.
There wasn't a huge difference in the results anyway, if you look at the actual figures in the graph axis, rather than the Bars which accentuate what is most cases is a small difference. If the scale was smaller it wouldn't look so dramatic.
What are a few seconds in the boot times, given a few months and a dozen installations, etc. no one will get those figures anyway.