I'm investigating using Umbraco 5 for a base for a portal site and was trying to fit my own libraries into a custom solution when I came across an error relating to a version issue with FluentNhibernate and Nhibernate.  I noticed that Nhibernate was two versions behind so reverted back my project to the older version and hooked up the appropriate FluentNhibernate implementation and still got an error on the FluentNhibernate library.  After some research I noticed that Umbraco 5 is using some customized version of FluentNhibernate 1.2 that has a version of 2.0.   It seems the library was customized to include a MergeSaveAllDeleteOption method that may be part of the new FluentNhibernate versions.  My question is why does Umbraco 5 use a custom version of FluentNhibernate and are there plans to move Umbraco to the standard FluentNhibernate versions.  It would be nice to have a standard library that you can obtain from Nuget so you don't get version errors.