I like them, I would struggle to give you any real reason to get them though. There well priced, reasonably well built, a ton of settings and configuration options, I don't think I will use half the functionality they have. I got them running quite quickly in analog speed mode. Compared to steppers they sound quieter, you get encoder feedback, potentially better high speed performance, index for homing and integrated power supply.

Main issues have been tuning the servo without dedicated software and documentation, i'm still far off on this and i'm not really taxing the drives which is a bit concerning. I know Clive has been having problems with large >1mm following errors on high speeds with step/dir setup and there are reports of several people having some interference issues with using them in step/dir.