Since Jorge referred you to the unblinkingeye.com, where there is one article about Azo and Amidol, I will refer you to the Azo section at michaelandpaula.com where there are four articles about Azo and there is also the Azo Forum, where there are many lengthy discussions about these things. Two of the articles are by the fellow who wrote the article at unblinkingeye.com and two are by me. I suggest you go there for much more information about this than you will find anywhere else on the planet. In any case, I will anwer your questions here. (At the moment there is a glitch in the Azo Forum and new topics cannot be added.)
1- Do Amidol processed prints need different exposure than Dektol prints? Probably. Any change of developer will require a change of exposure.
2- Does it change (Azo) paper color/tone? To what? No it does not change the color of the paper. It is what it is -- a neutral black, slightly green, as Jorge described.
3- What is the difference between Fein's and Michael A Smith? formulae - in terms of cool/warm/color to the paper? I do not know Fein's formula. Let me know in an off-line email and I will tell you (by posting here) what the difference will be. My next article in View Camera magazine is about the chemicals in developers and how each one affects the print--including how it affects the color.
4- How's Amidol for papers other than Azo. Is it worth swtching to? In my opinion, yes. Amidol gives deeper blacks than other developers. In my article, "On Printing," which first appeared in View Camera magazine, and which can also be found under "Azo" at www.michaelandpaula.com, I gave the formula for Amidol when it is to be used with enlarging paper. It is a different formula than that which is used with contact printing papers--meaning Azo--the last one still being made.
5- What exactly does extra time in it do (ie, 3-5 mins as opposed to 1-2). For Azo, increasing the time does no good at all. One minute should always be maximum. The best developing times for enlarging paper are a function of the paper and not the developer. Every paper has an optimum developing time. The last enlarging paper I used extensively, Velour Black, had an optimum time of three minutes,
6- Lastly, how "better" is Amidol anyway? Are we talking about a 10% improvement? 50% - 100%? You cannot put a % on it like that. Amidol does yield the best tones--longer scale and deeper blacks. Especially when used with a water bath it gives more control over development. It is also easier to use than other developers.
"I've got my breathing mask, gloves, long sleeves and fans all at the ready for this nasty - but highly touted - chemical." No need to overdo it. Amidol is not that toxic--not nearly as toxic as metol or hydroquinone. Wearing a nitrile glove on your developing hand is the only precaution that is needed.
There are no magic bullets, but the Azo/Amidol combination comes as close as possible to one. That being said, this past weekend Paula and I conducted one of our Vision and Technique workshops. Some of the participants brought prints on Azo that were developed in Amidol. Virtually none of the prints were really fine prints, or even very good ones. Printing requires much more than having the right developer or the right paper, although if you have those other things, then having the right paper and the right developer can make a gigantic difference.
Do I know what I am talking about? Recently there was this exchange on another forum--on a mail-server list. The discussion was about ABC Pyro. One respondent wrote this:
"There have been some discussions lately about using ABC, exclusively, with
LF negatives for contact printing with Azo. I have seen Michael's and
Paula's work using these materials and their prints are simply the very
best on Planet Earth."
I replied, "> Well Curt, many thanks for your kind words about our prints. Paula
> and I certainly make prints that are among the finest
> being made today, but the "best on Planet Earth?" We don't know about
> that, but we will happily quote you nonetheless. (which I have done here).
He then answered, "Well, Michael, you're just too modest. By all objective and subjective standards, the prints you produce are absolutely as close to perfection as
humanly possible. You are a perfectionist and a master of the craft."
My advice in any field of endeavor is to listen to those who have actually done the work themselves. Too many on various forums have many things to say, some of which may be quite useful, but without their having the work to back it up, much of it is also unreliable.
Good luck with Amidol and Azo. I do not believe you will be disappointed.