I agree with everything I have heard here; especially timeliner's comments. It's kind of a neat dive. It is a cold war relic although I didn't feel weird about it. Of course then again, I am interested in the history of those things.
I definitely would NOT conduct this dive as part of a certification. It is an interesting dive for one time. You really should be focused on the experience of the dive / dive site though. Don't be distracted with the requirements of a certification.
Timeliner does have a rattlesnake skin. I was there. I saw it.
Seriously, this is a fun little dive; but just do it as a fun dive. I will add this. The perfectly, smooth, round, grey concrete cylinder that is the silo can give you some interesting sensations of vertigo. With the cylinder being as described, you never have any real solid reference point for motion as you travel from surface to about 80 ft. There are a few exceptions to this statement but I don't need to clutter up the basic relevance of this statement.
Everyone should do this dive one time just because it is unique.