As stated already, they mesh perfectly, so much so that certain Warmachine armies can use certain units from Hordes (that is, if I recall correctly). And yes, seeing gigantic warbeast clash with enormous warjacks is an immensely pleasant sight to behold!
I really love the dynamic the two bring to each other when they are matched up.
Current Record: 4/10/2 w/l/d
I don't mind losing, it's fun either way!
Games I play: Warhammer 40k, Magic The Gathering, Pokemon TCG, Pirates CSG, Other random video games and TCGs.