I'm of two minds on Kore and Logic (I haven't used Kore with any other DAW platforms since switching to Logic). It has some useful features, but often it's still faster to use the plugin on its own with the mouse. This is especially the case with third party software.
There are times I'd say it helps my workflow, especially the Kore packs, perhaps a touch less so with NI soft synths (the way it interfaces with Reaktor simply baffles me).
At times the cryptic abbreviations on the screen and the controller's front panel make simply opening up the software's GUI and working there faster than using the Kore interface that is supposed to make this unnecessary.
For quite some time, Kore crashed regularly on my up-to-date system; I did discover that trashing the Kore 2 user prefs folder has helped a great deal, and it hasn't crashed since doing so in the past week or two, so there's a tip if you're having problems with Kore crashing when working with synths/software into it.
The Kore soundpacks are for the most part extremely well done, and I like NI software a lot, having most if not all of their soft synths/samplers.
However, Kore can be a little confusing when it comes to finding and organizing some of the metadata, especially when it comes to third party software. In many cases, it simply can't retrieve patch lists, etc., and you're stuck with lots of monkey work if you want it to do what you bought it for (unless you're running the free version simply to run the Kore packs).
Would I buy Kore again? Actually, yes, simply for its ability to run the Kore packs it's worth it for me, including the controller. But I would love to see NI improve a few things to make using the software a bit more integrated into the workflow.