I own or have owned several of these. The Kinesis Advantage 2 is the only one I regularly recommend. It's very expensive, but also refined, thoroughly tested, and highly customizable. It did not take me long to adjust. I'm now as fast on the Advantage as on any mechanical standard.
I’m used to flying through editors by muscle memory so it feels quite painful to stumble on the new keyboard. Half the time I have to look at the old keyboard just to figure out what the actual keys I wanted are.
Any suggestions to get over the hump? I’ve tried some typing games like Epistory but they normally focus on normal keys. I haven’t see one for these special keys.