My opinion on the chasqui scout, still I've already argued about it on the chat...
My thought is that this UU is bad.
The Incans are expansionnist, and so have to make the best use of their trait, otherwise they'll end up with one useless trait. Being expansionnist means to be able to build scouts that will quickly run through open land to search for other tribes and huts, and to safely pop up huts. The key is to quickly build some scouts without much delay and send them everywhere. Now we have the chasqui scout ; this unit is a warrior and a scout altogether, making it a superb unit, available from scratch ! Now this fusion costs 20 shields. STOP. Where is the blitz exploration ? What I wanted was to build scouts quickly so as to secure huts and meet the other tribes first. The Incans will be able to build super-units that can pillage easily, defend quite well, retreat... but they'll be late on the exploration front, their first mission... making the expansionnist trait of less value.
But it doesn't stop there. With more time required to build those super-scouts, not only do you let other scouts
scout faster, but you also delay your expansion ! Settlers will come later, etc... And you don't want to bring your old super-scouts back home for garrison duty, right ? So you'll have to build warriors or such anyway.
Fortunately, the Incans are agricultural, making it less bad than at first glance. Still, the expansionnist traist is partially wasted. Now, chasqui scouts will be able to trigger a golden age ! This will allow the Incans to build chasqui scouts faster, almost at double speed ! Well, if you're quick enough to find a foe to kill... And if you are, that will mean an ultra-early golden age. And if you really want to build chasqui scouts quickly, you'd better have an ultra-early golden age, because you don't want to build chasqui scouts for ever.
So the Incans are forced to get this kind of golden age if they want to profit a lot from their characteristics, making them an ultra-early civilization... or a crippled one. And ultra-early civs aren't the best ones, or I could say that it's better to have the choice. See the Greeks : they can have a golden age very early, but can also delay it till the Middle Ages or later
without crippling their expansion.
What that really makes me think is to be able to build both the UU and the unit it replaces. I'd like to be able to build standard scouts as Inca if I want. I don't care if they are killed (I mostly think of solo games here). When they are killed, most of their job is done. And 2 scouts is always better than 1 super-scout.
Of course the Greeks won't build any spearmen, because hoplites are better in any point. But what about gallic swordsmen (50 shields !!!), sipahi (80 shields, less impact) and so on...? The worst thing is that the chasqui scout is directly associated with one of the Incan traits, so that you're almost forced to build it... or you waste a trait...
OK, 20 shields may not sound a lot. You'll delay your expansion by a few turns, it's not the end of the world. Well, play Sid level and you'll see.
It's a matter of turns. Agr/Exp sounds appealing, but sorry, the chasqui scout does not... Maybe it is intended : make a not-so-good unit that look good to some people ?
I'll be very glad if some people counter my point of view.
Don't hesitate. And don't forget this is only MY point of view, based on what is known right now. Other things will surely have changed, they said so.