i did the sligachan route last week. had heard a few things from this forum- checek out this thread:
http://www.singletrackworld.com/forum/topic/a-few-pics-from-the-sligachan-loop-last-week-its-no-half-bad-like
from what i could tell, the route works better in reverse if you want to do a circular route. But tbh it is probably better as an out and back from Sligachan.
We decided that the Strath Mor section sounded miserable so we went for the slightly longer Strath Beag path. However, after a short initial rideable section, the path soon became unrideable, with a 30-45 minute hike-a-bike. However, after this section, the riding was superb with only a few short hike-a-bike sections. I do not know how the Strath Beag path compares to the Strath Mor section, but it was pretty wet when we were there and so a boggy section didn't sound very enjoyable. The Strath Beag path was pretty solid for the most part. There is also a nice cafe once you return to the road with a friendly guy who seemed very keen to find out where we had been riding as he didn't know of any paths suitable for bikes!
The return leg on the circular route which i did was back through Glen Sligachan was awesome, and we felt that although you could have a good run coming the other way, it was probably more fun doing it the way we did it.
If you decide to do it the same way as talked about above (i.e. Strath Mor section at the end), you will be greated by a beasty road climb back to Sligachan Hotel which would possibly spoil what is otherwise a great route, and certainly among the most enjoyable i have done.
Let me know if i can be of any more help, could probably get a memory map route map for you, or failing that just a picture of the route we followed.