I just upgraded a friends Acer laptop last week from Vista to Win7 with the Acer official upgrade disc.
This disc is just a bog standard Win7 upgrade disc
AFAIK but with Acer branding rather than MS, so you do need a Win7 upgrade license key to use it.
Also the 'free' upgrade disc had to be bought (cost £20 IIRC to cover postage and handling costs

) and was only available for a limited time from Acer. So if you now want to upgrade I think you would need to buy a Win7 upgrade from your retailer of choice.
Mark.