I could never speak a bad word about these games as they were a big part of my childhood and succeed wonderfully in what they set out to do.
One thing to consider before buying these though is that Activision, the company now holding the King's Quest license (and responsible for bringing these to GOG) recently shut down a fan-made King's Quest project called "The Silver Lining". This was a project that had both the blessings of the creators of Kings Quest and a legal agreement with Vivendi (owner of the IP before they were gobbled up by Activision) which authorized them to develop and release the game to fans for free. The team behind it therefore continued to pour years of work into it without fear of legal consequences.
Now, after 8+ years of solid work on the project, Activision have decided not to stand by the agreement that was in place with Vivendi, and have (with a 'cease and desist') ordered the project to shut down and remove all assets from the internet. This is a crushing blow to these dedicated fans and to King's Quest fans in general, many of whom have been supporting and anticipating this fan game for almost a decade.
I apologise if this is not the place for this sort of thing, but I feel it's important for King's Quest fans, new and old, to be aware of this. If your beliefs are such, show support by signing the "Save the Silver Lining" petition a quick google will find, perhaps write to Activision, and give some thought to whether or not you wish to support Activision's decision with your money.