Well, this is a little hard to answer. The Profantasy website has links to a few different people's websites that use cc3 and cc3+ Then don't forget all of the add ons to the main program that allow for even more types of mapping. Also, how is anyone supposed to know what you personally would consider impressive? Are overland maps impressive to you? What about dungeon maps? Or star system maps? How about perspective maps? And then there are diorama maps?, and city maps? The list goes on and on.
Lets not forget about people's skill level with the mapping software too. I don't consider myself a great user of cc3 or cc3+ but other people like some of the maps I have made. There is a guy on the Profantasy forum named Joachim de Revenbel who runs circles around me when it comes to mapping and has made some things I consider very impressive. There is a woman on there named Shessar that has made some maps I considered very impressive as well. But maybe my tastes in mapping differ from yours.
So how can anyone really answer this question? I can only tell you that I love the program, even though it takes some getting used to. And I know I am not utilizing it to its full effect so my maps have been suffering for it. But learning everything you can do with it takes time because it really is a full vector graphics piece of software. The tome of ultimate mapping, the book that tells you how to do it all, runs a good 619 pages. Some of it gets quite technical, especially the part about making macro's. (Note that you have to buy the Tome of Ultimate Mapping separate from the program, just like you used to have to do with Photoshop if you wanted all of the technical details of that program.)
And don't forget, Mike Schley has both an overland mapping style and a dungeon mapping style that cc3+ and dd3 use.