[Update]: The anniversary patch has now gone live, and it sure is a big one!
Even though Starcraft 2's Map Editor is significantly more powerful than its Warcraft 3 counterpart, using it requires unusual amounts of effort. When I first tried to make a map, and this was after years of playing around with Warcraft 3's editor, it took me well over an hour to figure out how to change a single character model! Needless to say, things like that aren't exactly ideal for a tool that's supposed to be fun for everyone to mess around with, regardless of their experience.
With that in mind, you might be glad to hear that all of this will soon be a thing of the past. It may have taken quite a while to get here, but Blizzard is now finally implementing some massive improvements to the Map Editor, many of which are inspired by Warcraft 3.
Not only will the new Starcraft 2 editor be significantly easier to use, but it will also be getting a variety of upgrades and tools to experiment with, all of which will greatly increase the amount of possible game types and map designs. For example, you will be able to make absolutely enormous cliffs, boats that actually sail on water rather than awkwardly fly over it, make units march in formation, and the list goes on for a while.
There really is no easy way to summarize all of the changes, so if you're curious, make sure to head on over to the official patch notes to learn more. Do bring a cup of coffee before you dive in though, because the list really is stunningly long. Enjoy, it really looks like a great bunch of changes!