My upgrade to W7 cost about $250 CDN and I put it off for long enough but recently bit the bullet on it - as much as I detested doing so, if just for matter of principle. Rather an expensive fix to a tainted OS IMHO.
Further to this upgrade, even though I went through the system check at Microsoft that basically told me all of my software would work just fine on W7, that has not been the case, and I have incurred additional upgrade costs and headaches.
Today's upgrade was with Dragon Naturally Speaking, where my 9.5 preferred version is no longer working with W7. They smacked me for $120 to upgrade.
If you have had any unsuspecting upgrade requirements, or just plain time-wasting headaches due to switching to W7, I ask that you list them here so that others considering such, might get a heads-up for the real cost of upgrading.