No, but I've been typing on one for five years anyway.

The concave keywell shape of the Dactyl Manuform is more ergonomic for me than flat keyboards, even when they are tented with an opening angle. (I had a two-piece flat keyboard, the Keebio Fourier, before this Dactyl Manuform.) I expect it to be more ergonomic for anyone.

The thumb area of the Dactyl Manuform is constructed with the idea that you will actuate the keys there using the pad of your thumb, not the side. The original Dactyl and the Kinesis Advantage 2 have a thumb cluster which is raised up relative to that of the Dactyl Manuform, and I think this is more correct.

With your HHKB and Realforce collection, you might be interested in the Dometyl, a keywell keyboard made to support capacitive rubber domes. Its three thumb keys are probably angled better; but I have not yet finished building my Splaytyl (another variant in the same repository).