Sorry for the bump but I thought I'd add in my 2p.
I had the same problem with the "bumpy" and concave ceramic side. I didn't know that this issue was meant to settle itself out over time so got in touch with Fallkniven and after some emails back and forth they said send it in. Sent it recorded international on Monday morning, got a new one through Saturday morning.. Couldn't be happier. Admittedly I might have got to it a day early since I work for RM and picked it up as soon as it came to the depot but still, I'm chuffed.
To anyone doubting the quality of this product, there customer service sure is great!
Also, just an observation, the new DC4 sent to me is the new variety (they told me to wait to send it in until I did as they would be receiving them then) and the ceramic side seems MUCH nicer than before.
Also, this has been bugging me for agggges!! .. What is that hole for in the diamond side?!