Yes, the Mirror Function is still there albeit under a new updated Icon, as shown below, first NX 6.0 and then NX 8.5:
Also note that the selection order in the dialog has been reversed and that you now can use selection intent, such as 'Connected Curves', 'Tangent Curves' or 'Curves in Group' as well as 'Single Curve', so that it's easier to select a profile with many curve elements. You now select the curves to me mirrored first and then the 'centerline' reference.
John R. Baker, P.E.
Product 'Evangelist'
Product Engineering Software
Siemens PLM Software Inc.
Digital Factory
Cypress, CA Siemens PLM: UG/NX Museum:
To an Engineer, the glass is twice as big as it needs to be.