Cool question, here is my two cents:
Someone that often specializes in one specific area maybe or more for example: Instructional Design, Teaching, Technical Writing and use of a rapid development tool.
Someone that can truly claim one-stop-shop and wear the following hats with ease:
1. Instructional Design
2. Programmer – (Actionscript, PHP,ASP,PERL,JAVA)
3. Curriculum Developer
5. Network Expert
6. Hardware Expert
7. Developer – (Articulate, Lectora, Camtasia, Captivate)
8. Technical Writer
9. Voice Over Artistic
10. Graphic Artistic
11. Video Editor
12. Project Manager
I guess bottom line a Guru has more experience and can wear many different hats within the entire ADDIE Cycle. A specialist would normally have less experience and feel comfortable within a particular part of the ADDIE Cycle.
All the best,