I use Phase One's Capture One and Photo Mechanic.
I personally prefer C1 over either LR (CC) or DXO 11, which I also have. I never use LR now, but I still occasionally run DXO from C1 to access DXO's Prime Noise Reduction. I especially like the colour controls and the layer based local adjustments in C1, plus the overall image quality that C1 seems capable of.
I have used Photo Mechanic for years, primarily because LR was very very slow for file management and Photo Mechanic is very very fast, even slow computers. But, its really aimed at press photographers or similar, who need to rapidly turn round photographs at events and while its really useful to have around for organising images, captions etc, I'm not sure its "needed" by most people. I'm not sure there is much (anything) it can do that can't be done in LR or C1, its just a lot faster, and more convenient, to do it in Photo Mechanic.
They are meant to be adding a Database to Photo Mechanic, but this has been ongoing for years and years, but they are hinting it might now be imminent.
C1 cataloging is OK, and improves with each point release, but I find the catalogues very slow to load, and have a catalogue for each year. Once loaded, however, I find they run well enough. C1 also has the option of sessions which allows you to work on a project by basis with all your originals and derivatives managed by C1 and kept together in the same folder.
For a "global" catalogue, I use the low cost and very good Neofinder. I also use Phase One's Media Pro for this, which is blazingly fast and offers some integration with C1, but Phase One break the integration when they release a new version of C1, and take months (years?) to fix it.
Cheers,
Graham