The Kong drum machine was introduced to Reason in version 5. It can generate its own drum sounds, offering a lot of real time flexibility via its plethora of knobs. Even if you just want to use these internally generated sounds by themselves, it's already better than most drum machines, even giving the legendary (and still expensive) Roland TR-808 a run for its money, although it's still not going to replace the other two nineteen eighties classics, the Linn LM-1 and Roland TR-909.
With all this self contained functionality, it's easy to overlook Kong's sample playback feature. Personally, I'm not completely replacing my drum machine sample CD with Kong, but I'm certainly replacing ReDrum, as Kong can play back drum samples in a way which acts like ReDrum on amphetamines.
First, it has sixteen channels instead of ReDrum's ten. Second, you can label each of these channels, so that when you're drawing notes in the main sequencer, you can actually see whether you're drawing them for the kick drum, snare drum or whatever else you've loaded in, rather than the unhelpfully titled "channel 1" onwards. Third, it runs circles around ReDrum's "channel 8-9 exclusive" button, commonly used to make open and closed hi-hats cut each other out, by giving you three separate groups of mutual exclusivity and letting you put any of the sounds into each of these groups.
So although I'm not getting rid of my drum machine samples just yet, Kong's own sounds offer great flexibility, and its sample playback is a nice refinement of the ideas introduced with ReDrum back in Reason 1.