A few things to do:
1) Drummers don't hit the head with the same strength each time. Randomize velocity by about 7-10% up and down. You may have to manually adjust a couple of points, but randomizing the velocity on your drum tracks goes a LONG way.
2) Drummers don't hit the head in the same spot all the time. Use multiple samples for the same pad to achieve this effect. Dont know if it's possible with your drum software, though, as I am not familiar with it... but if you use two (or more) slightly different samples, this can help as well.
3) Add a REAL human touch! I tend to almost always use some sort of real percussion in my recordings to give it more of a human feel. That is, I set up a mic, and record myself playing tambourine, shaker, djembe, etc...
4) As mentioned earlier, drummers tend to throw in ghost beats as well. It doesnt hurt to slide one in from time to time.
I should add that I use Session Drummer 3 for most of my projects. I occassionally use Battery. Both are great soft synths for drum tracking, IMHO.
Hope that helps!