Well, I'll jump in here with my 2 cents. If you want an exact replacement for your acoustic drums, there aren't any. If you are looking for a highly portable midi controller with what I would consider to have one of the best and most sensitive triggers, then that would be the Zendrum. Another comment I would make is that your sound source becomes critical when you want sensitivity and dynamics for percussion/drums. If your sound source can't respond, then it won't matter how dynamic you are with the midi controller.
Using my Zen and a Fantom X Rack mount unit has given me the best overall dynamics I have ever had with electronic drums (been using electronics since the mid-80's). There are many options on this board for excellent sound sources such as BFD and a Muse Receptor (if you have the money to spend).
However, playing a Zen is not at all like playing a drumset or any of the drumpad/trigger setups sucha s the Vdrum and/or DrumKat where you use sticks. On the other hand, you get a LOT more control over velocity using your fingers on the hard plastic Zen midi triggers than you can using a pair of sticks.
...Just my thoughts