I have to say several things:
No one is really running vista these days as even Windows 8 is slowing encroaching on that marketshare. Microsoft secretly hates it and wants to get rid of it as it is literally a fail for them and something they want to pave over. This is also similar to what they've done with xp, not porting over IE 9, not building Office 2013 for it, and I think a couple of other things as a) in technological years it is a dead cat and b) it's not terribly secure as a system and Office 2013 would simply look disturbing on xp in my opinion.
Doing the claculations, Office 365 is a better deal than just 2013. If you buy the latest version that gets released every few years, you end up saving considerable money with the new price structure. The Office apps that come with the 365 Home Premium version seems to be the same as Office 2013 Professional Plus, which retails for 400 dollars. Office 365 Home Premium is that for 100 dollars a year, or 10 dollars a month (which I bet would be real nice for students as they probably would only use the software certain months out of the year) along with 20 gigs of SkyDrive storage which would be 410 dollars with 2013. With 365, it seems you will also be upgraded to the latest version of Office for free. So in three years, 300 dollars for the equivalent of 2013 Pro Plus and the separate SkyDrive storage which would be 410. One hundred and ten dollars of release cycle savings. So when comes time for Office 2016, you'd still need to use Office 2013 Pro Plus for an extra year before you get that benefit of 365, THEN pay the 400 dollars again to upgrade to 2016. Except 365 allows for 5 PCs whereas you'd have to pay 2,000 dollars for the same with Office 2013 Pro Plus, so actually, your savings would end up being 1,700 dollars per release cycle of three years if you use the 5 PCs.
So basically, using 365 allows you to use the software on a monthly basis, or year long basis; gives you 20 gigs of extra SkyDrive storage over the base 7 gigs, you get the latest version for free, and you get the whole Office suite as well. All in all, 110 dollars of savings. Seems legit I'd say. There isn't much of a rational argument against it as the software is natively installed on the PC, for five of them, documents can either be saved to SkyDrive or natively on the hard drive, and you get settings and custom dictionaries transferred over as well as SkyDrive documents. Faster, easier, better, and cost effective, along with preventing piracy to an extent.
One must not underestimate Microsoft, when it comes to business, they KNOW what they're do for real!
