I received a trial version of it to use in connection with a workshop I took last month (Momenta's Project LA -
Momenta Workshops | Project Los Angeles 2014 ). The instructors (all with backgrounds in photojournalism) raved about it and I could really see the advantages of it in the demo they ran for us.
Unfortunately, I had some difficulty to get it set up on my PC (my instructors were less familiar with PC than Mac) and, as a result, I never got it to interact seamlessly with Lightroom. We were under such time pressure in our daily edit and processing sessions that I didn't get a chance to get it sorted out, so I never managed to run a good test. I definitely could see how it would be really useful when you need to quickly upload a very large volume of images and then select your picks (e.g., a wedding photographer). Those familiar with it also said its coding system works well when several people are uploading images to some kind of shared folder (for example, several journalists tagging photos with labels specific to the individual photographer and also to the specific project - then an editor can review images by project and individual).
For my work, I rarely upload more than about 300 images at a time, so the upload time in LR on my computer (usually about 5 minutes, rarely more than 10) isn't a problem. There is much more to PhotoMechanic than the speed with which it can ingest a card and give you images to review, but this is one of the key benefits and it's not that important to me at the moment, so I don't think I'll keep it after my trial ends.