I came across one guy who was certified and he had very bad habits and did not know how to properly use and modify XREF entities.
Autodesk certifications (at least for Autocad) are quite useless. They test whether or not you know what commands to use, how they work, how to modify objects/properties, etc, but they don't teach anything about best practices or "the right way" to do things. Mostly this is because there are 20 different ways to do any one thing in Autocad. One company will use a particular system and another company will do it entirely differently.
For some software, a certification may carry respect. AutoCAD certifications would not, imo. I've never talked to another CAD manager or engineer who cared for them, either, so I don't think my opinion would be too terribly rare. I believe it is a combination of the very nature of AutoCAD software and it's versatility, as well as the nature of the exams themselves and what they require for a passing grade (not much).
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NX8.0, Solidworks 2014, AutoCAD, Enovia V5