You may get a lot of replies and debating on this subject...
I, for one, love the Kalamar setting. I started DMing in my own world and then moved to Greyhawk later. When FR came out with 2ed I switched but I soon became disillusioned with FR and with D&D so I stopped playing. When 3ed came out I bought the three core books and looked it over. I debated as to whether to start a new D&D game but I just couldn't bring myself to do
it. The GH gazetteer came out and I scooped it up and read over it, happy that D&D would now be "based" in GH. But, I guess over the years even GH seemed stale. Then the Scared Lands books started coming out, but I did not want to play in a cataclysmic world so I resigned myself to just keep on playing Shadowrun. Then Kalamar was released. I looked at it and, even
though it is not a "pretty" book it looked interesting. After reading it I was hooked.
Kalamar is a well thought out world that is human centric. Yes, there are other races present. There is even a kingdom ruled by Hobgoblins. There is information on the expansion of the human race and how they settled in each area and how living in that area created the culture that now exists. There is a real feel of "History" with this setting. As I read though the book,
plot hook after plot hook jumped into my mind. After the first chapter or two I realized Kenzer Co was giving me a wonderful setting and at the same time giving me plenty of room to run it the way I wanted to. It was like my beloved Greyhawk but, Mr. Gygax forgive me, better! The world was not made as characters ventured out from a starting point, it was made by thinking how life would evolve first and then they worried about where to place
characters. To me, Kalamar is a "realistic" setting.
I think you would like it if you tried it. If you are not sure about
spending the cash I would suggest buying "Root of all Evil" first. It will give you a good introduction to one part of the Kalamarian world. There are several chapters in the setting book, each detailing a different area of Tellene and each section presents a different culture and feel.
So far my players and me are enjoying the setting. Better designed than Greyhawk. Not as high fantasy as Forgotten Realms. It is not set in a post cataclysmic environment like the Scared Lands. No "steam punk" aspects like Iron Kingdoms. I have not seen Paradigm's world, so I can't compare to it.
"Realistic and Gritty?" I think it would fit your needs.