Is moving Adobe CS from PC to Mac painful?

Do not think straight out that you can just purchase the upgrade of the other OS version, and expect that your upgrade license number would work with it.  It won't.  Why do you think is it so hard to migrate applications between platforms?

Well, for one thing, it's not that easy for software vendors to do that.  It's almost like when Adobe and Macromedia competed with each other that web and graphics designers had to decide on whether to go the Adobe or Macromedia route.  Once they committed to their software of choice, they were committed.  Deciding to switch would mean to give up the initial cost of their original purchase and shelling out another $2000 to get the other suite.  Even if the companies accepted their competitor's licenses, how could they even verify that the license were legitimate to allow their customer to purchase the full suite as an upgrade.

With Vista tanking in sales, and Microsoft man-handling their vendors to sell Vista, its no wonder so many people have switched to Macs: including myself.  And all who have switch, would like to move all of their software over as well.  Certainly, Boot Camp and VMWare Fusion or Parallels would offer a short-term solution, but it would be nice to be able to run the software natively, and not have to be dependent on multiple OS for an end-user's solution set.  So many have requested that Adobe (mainly) and many other vendors to provide a way to move their licenses over to the Mac.

First of all, Adobe is not obligated to provide this to their customers, but if they didn't, it would put them in the same boat as Microsoft, and piss off their loyal customers.  Because the licensing structure was probably created differently in each of the OS implementations of the same software, it would have been hard to have had the ability to create cross-license checks.  So the reason why Adobe is asking you to "destroy" the software (hence the Letter of Destruction) is because they are essentially giving the end-user a completely new license for the price of an upgrade (hence the reason why the switch is only eligible to upgrades and not cross-version).

So Adobe is taking extra steps to provide a solution to your problems, as they are asking us to take extra steps to ensure that certain things are in order.  A little pain for long-term gain.