Having rediscovered yerba thanks to this thread, I have fallen in love with it and have been drinking it almost every day to very beneficial effect. It makes me feel good and be motivated in a work situation, and makes me chatty and interested in a social one. Without it, I am often easily bored and unmotivated.
Now, the reason I had previously avoided it was because I can't stand caffeine.
-COFFEE makes me really edgy, jittery almost paranoid.
-TEA (the normal stuff from India) is better because I remain calmer, which may be due to the lesser caffeine amounts or perhaps due to this calming teanine stuff that they tout as it containing on the packs. However, it's effects on me are mild and I am neutral on its usefulness.
-CAFFEINE PILLS give me similar effects as coffee, but without the horrible taste and stomach trouble, and I feel a little more energised. Still, I don't like them. I have used them many times.
-YERBA MATE, however, is very different and a lot nicer. At traditional levels of consumption, I get very stimulated but I actually enjoy the experience unlike with coffee. There is still too much caffeine for me, and after a couple of cups I do find myself start to get too jittery to work and crash a little, even if I am feeling good. I have since realised that lowering my dose to just a cm or so of yerba in a mug is best for me, whereas before I was drinking a mug 1/2-3/4 full of chopped yerba from a pack. I still get the feelgood and sufficient stimulation, without the negative effects that I associate with coffee or caffeine pills.
I believe there is a chemical other than caffeine in yerba that is either (a) counteracting the negative effects of the caffeine such that I can enjoy the experience, or (b) making me feel good and perhaps stimulated also of its own accord.
Finally, I have also noticed that I am at least paying more attention to sound. Sound and music in particular sounds clearer and more interesting, although this could be just because I am actually listening for it. It's a bit like how when aya first starts coming on sounds become very noticeable, but it does not go as far as when they start to sound altered psychedelically. It's possible that it's placebo because I had already read this thread. I can't say if I get this with caffeine alone, because I hate the stuff and the only time I take caffeine pills is when I've been up all night so everything is weird due to sleep deprivation anyway.
Finally, though I used to think the stuff tasted nasty, I now love the taste and more importantly the smell. It has a sweet malty smell that excites and pleases me. What do the two chemicals you highlighted smell like, Ron?