Very flexible. Many many settings you can mess with but that can get you in trouble quick also. It is very fast on slicing.
On one of my printers I can do a print with the supplied software (it is free so it is what it is!) and the print is ok. The same print in S3D is much better but there is a lot more to know about using it.

The response I usually see is people love it. Some have not liked it at first until they got things set up right and got an understanding of what all of the settings do and how they can affect each other.
There is a good support forum, it is not monitored by S3D but many members.
S3D support has been good and responsive for me.

Bottom line, I have had a good experience with it. It may not be for everyone. I am sure the other packages have their strong points also. There is no ultimate solution but maybe in time you find different slicers can be better at different things.