That's a very broad generalization - borderline trash talk. Too slow for what? Material managers? UV tools? Exporters? Auto-riggers? I have worked on everything of that except the latter (rigging is not my thing) and I've never had any performance problems what so ever. The real benefit is that developing tools with PyMEL…
I like the idea of Pymel, but I have found that it is way too slow for any real production use. I used to work with it all the time, but as my code grew, the sluggish performance became quite noticeable. If you are having to switch to OpenMaya for most procedures to speed up performance, I don't see what the real benefit…
No trash talk, I was just stating that the performance does not suit my needs for production and I no longer use pymel for that reason. I don't see readability as an issue, if the implementation is difficult to read, you can always wrap up stuff yourself by writing your own functions or classes and comment on what you are…