A chorus that comes up a metronome marking or two can increase the realism of a track. Don't feel you have to go back down to your original tempo thereafter. Try raising the tempo again on the next chorus. The application of consistent dynamic tempo changes is a skill in itself. Make several passes at your tempo adjustments until you're happy with the song's ebb and flow.
Dynamics can add a human feel to the groove.
If executed poorly, however, dynamic changes can be an annoyance. There are a couple of obvious candidates for variation in volume, each requiring its own types of subtlety. Programming the ghost snare beats is very difficult. If your drum loops require this type of subtlety, consider using MIDI or audio samples instead. Generally, these kinds of sampled grooves have the right feel in the ghost notes.