When trying to search something it would be a great feature if file-type groups like 'Source Code', 'Executable Files', 'Web Pages', 'Documents' or 'Emails' could be excluded from the search.
Especially the differentiation between sourcecode and documents would help a lot because sourcecode often has a much higher number of keyword occurrences than associated user manuals or other documentation.
Currently this can only be achieved by individually selecting all applicable document types. Creating groups would make this task much easier.
I'll keep this in the back of my head, although it won't be implemented anytime soon due to lack of time.
The ability to customize the file types used for filtering has been implemented in DocFetcher Pro.