You should have no major problems as long as you do some research..
However, some drivers that have been supplied for inclusion in the Vista installation are still in their infancy.. this applies particularly to video drivers.. some are better than others, and you may well find that you do not have all of the features to which you are accustomed..
Since the release of Vista, some manufacturers have endevoured to produce better drivers, so a visit to the various manufacturer websites can prove beneficial..
Re. software.. a not inconsiderable amount of software does still work with Vista.. if Vista reports that software should be removed prior to installation, one should NOT attempt to re-install it after Vista is on the computer.. in other cases, software may run ok but have maybe one or two minor issues.. it can happen..
It is not a bad idea to visit manufacturer and software websites to check out any known issues BEFORE installing Vista.. this should be done before any move from one OS to another..
What you, or anybody else, has to do is decide how important some hardware and software is, to either your enjoyment, or to anything ‘mission critical’ within your operation.. if all appears well, then you are in a position to upgrade..
Bear in mind that the Vista Upgrade Advisor is only as good as the information for which it is aware.. if driver manufacturers and software autthors have not supplied 100% correct info to Microsoft, the Advisor MAY appear to have been misleading in its findings..
Any future software or hardware under consideration for purchase by you AFTER having upgraded to Vista will need to be researched before you pay out money.. in many cases, there is a fix of some kind, but not always..
A case in point is Nero 7.. this software is ONLY 100% compatible with Vista from version 184.108.40.206.. this may not be the version contained on the CD from the store purchased box, depending upon how long the box has been on the shelf.. there is a full downloadable version on the Nero website for people who have already purchased a FULL version of the program suite from either the Nero website or a store.. the OEM versions as supplied with OEM CD/DVD units do NOT qualify..
The same kind of situation applies to hardware, where the installation files on the supplied CD may not be the latest drivers for the latest OS..
ALWAYS check first before buying.. CAVEAT EMPTOR.