We have been using it for years.  We do have older versions of the modules, so  I can't comment on any of the newer/current programming.
Many of our products are configured and before we used F&O, this meant creating dozens of different BOM for each combination.  Using F&O eliminates that, plus it makes updating BOM''s a lot easier.
In our old version, there is a field in the database file for a code for the Feature or Option that is not used.  It would have been nice to have this, as it would make sit easier when you are entering a Sales Order from a configuration.  As it is now, you have to be pretty knowledgeable about the products.
Our version is pretty manual, in that we manually type in the configuration in the description column of the base item and then choose the appropriate F&O's from the selection screens.
We then type in the  option descriptions, as most of our subassembly descriptions might not make sense to a customer.  
Ideally, it would be nice to have a configuration automagically entered (i.e., you enter the configuration number and the other sales order lines are entered by EVO.  An then have a separate description for each F or O that would be easy for the customer to understand.
If you take your time to plan things out and have a logical order to your configurations, it is very useful.
Some pitfalls-  If you make a mistake, you have to delete everything and start over. Also there is no logic (at least in our old version) against entering incorrect configurations (We have a configurator on our website that does that for when customers request quotes).
I don't know how much work has been done to the F&O modules, but this was one of the main reasons the boss stopped paying for updates.

FO-B : replaced the older report it was using with a newer one. The report now prints in my testing.  Thanks again that one.
 
Now something else:
 
SD-L (Features and Options Defaults) is supposed to allow us to enter a default duplicate
option code, as per the web help:
 
If you plan on using the duplicate options capability, you can select a default duplicate option code.  The values are.
 
1 = Display options - regardless of duplicates.
 
2 = Do not display - add duplicate to order.
 
3 = Do not display - do not add duplicate to order.  
 
The only thing we can enter in the setting is either Y or N.  Is that correct?
 
Version of SD-L (comes up as DEF-L) 12/23/16.
 
Kind regards,
 
Val