has it improved any of your metrics? (CTR, ROI, CPC..)
No. But, the insight it provides allows you to impact the stated metrics in a positive way.
If you already have complete back-end tracking matched to Google's cost/volume/position data per keyword - it's inferior and not at all needed. If you don't, or would like a "second opinion", say, it's worthwhile and nice to have within the interface...