We did find equations very useful pre 2012, but since Configured equations were introduced we have hit a few problems.
We use equations to create a fully automated design that has many equations and differnt configurations and it is stored in our WPDM vault as a reference set.
We Pack and go that reference set using "Select and replace" (replacing 1000 with the current job number i.e. 7726).
The first issue with configured equations, any equation which is set configure specific doesn't get renamed to 7726 when you open up the document, only equations set to all Configs do!.
My second issue is that if you have an assembly with an equation driving a dimension of a part i.e. controling its length, and that part is suppressed in another configuration in the assembly. When the assembly is saved colsed then re-opened the active configuration is built but not the configuration with the suppress part, so the equation errors and says it invalid.
this is becuause the part is suppressed and SW cant find the dimension to calculate the equation. I have to flick between configs to clear the error.
Using configuration specific equations doesn't work, still errors. I'm not sure if it's becasue the assembly was done in SW 2012 and converted to 2014 that its causing the problem, but there is no design table in any of the parts or assembly that the help file suggest is the problem.
The work around I'm using for both issues is select all configs for all my equations, and the configurations are set using hide parts with exclude from BOM and linked display sates. That way everything can be calculated ignoring the use of configred equations, also the Pack and go issue is avoided.