I use a NJB3 and the MicroTrack, and I really enjoy the MicroTrack. The recordings have been great. I tend to record live music in clubs or arenas or wherever it need be. I have done all the firmware upgrades, they have made the machine perform noticably better, The unit is now very stable. I have an issue still with the fact that you cannot fade the tracks out, and in a very loud environment, that means clipping even at the lowest recordable level. The good news is that even when clipping is visible, the sound is clear and undistorted. I can only assume that the ability to go lower will be dealt with in a later firmware, as it makes no sense that you cannot fade to silence.
That said, I really am enjoying the MicroTrack, the recordings seem to sound cleaner than the NJB3. If you look at the negative comments closely, most of them are by people who have not yet even purchased the unit, or by people who have specific problems with their set up, and understandably they want those issues dealt with.
It is safe to say there will be other firmware updates; M-Tek has made it clear that they want to keep improving the hardware which is easily done by upgrades to the firmware. Each fix has been worthwhile, and the installation is simple.