Skimmer: As you ask the question, it starts out like you really want to see the point of view of a Witness, but then the question seems (I don't know if that was your intention), but it seems like ridicule when asking "is the spirit-direction" of poor quality?" and "Is it intermitent?".
Whateve the intentions are behind the question, I will try to answer, although I expect some ridicule and some comments such as "I'm blinded", "you're an idiot" and things of that nature.
First, Yes I believe the faithful and discreet slave is Jehovah's only true channel. This is based on faith. I learned many Bible truth's through the FDS. Although, there have been updated information as our brothers investigate the scriptures closely, the basic truths that I was tought have not changed. Yes, other religions might get some things right (some do not believe in a fiery tormet, or the trinity, etc.), but they are not organized as Jehovah's people. I belive Jehovah is a constant and organized person and as such, would have theocratically organized people doing his will.
I also belive the FDS is guided by Holy Spirit in the sence that base their doctrines in the Bible which was written with the guidance of Holy Spirit. I also believe that each reader of biblical literature published by the WTS should look up the scriptures for the basis of the information. I also believe that one should not be stubborn in thinking that try to get ahead of Jehovah's appointed FDS. Instead, I humbly wait on their guidance and although I have my own ideas and thoughts, I realize that Jehovah has not chosen me as part of his FDS. See, Jehovah is a God of order and he has his reasons for doing things the way he does. I am nobody to question his ways.
Big Jim wrote something interesting:
By stressing the need for an organisation to teach the Witnesses and guide them in their thinking and conduct, the Watchtower Society effectively usurps the role of the Holy Spirit who, as Jesus promised, ‘will teach you all things’ and ‘guide you into all truth.’ (John 14:26; 16:13)
If this is true, why did the apostle Paul travel to the congregations in the 1st century? All those brothers and sisters where annointed with holy spirit, but they needed the guidance of those that Jehovah used to give them food at the proper time.
Similarly, today the FDS gives counsel and helps us keep up to date with Jehovah's word and ready for trials we must encounter.