I do have a Sesto Senso focuser and I did have it on my ES 127ed. It has since been replaced by a ZWO EAF....much better product. The Sesto Senso is on my Televue now.
The Sesto Senso took some work to make it usable on the Hex Focuser. I have since replaced it with a Feathertouch. The ZWO is definitely the way to go as it is cheaper and it operates on the focuser main shaft rather than the slow motion shaft like the Sesto Senso. The slow motion shaft is a planetary so there will almost always be some slip which will effect how precise you can get your focus routine to run.