Gonzalo Fernández de Oviedo, the great chronicler and naturalist, devotes an entire chapter to the chili, which is called "ají". He also describes other peppers that are not hot, but in general he has a very high opinion of the chili, and so did the rest of the christians, according to him. Let me translate a couple of paragraphs, as he is very good explaining this:

About the ají, which is a plant which the Indians use instead of pepper, and even the christians have it as a good spice

Ají is a plant very well known throughout these Indies, islands, and firm land, and useful and necessary, because it is hot and gives a very good taste and appetite with other foods, both for fish and for meat, and it is the pepper of the Indians, to which they pay a great deal of attention, despite the abundance of the ají, because they plant it in every farm and orchard with much diligence and attention, for they continuously eat it with fish and with the rest of foods. And it is not less grate to the christians, nor they do less than the Indians because, besides it being a very good spice, it gives good taste and warmth for the stomach; and it is healthy though very hot this ají.

It is a plant as tall as a man's waist, and there some ajís that are taller than a very tall man; but on the matter of size, a lot depends on the soil where it is planted, fertile or thin, or how it is watered; but, commonly, the ají is five to six spans tall more or less. And they have a topped base, with many branches. The flower of the ají is small and white; it does not smell, but the fruit is in different manners and sizes, and every ají burns a lot, like pepper, and some even much more.

Father Acosta, some 50 years later than Oviedo is of the same opinion, even pointing out that the spicy part of the ajís are the seeds, and concurs with Oviedo that chili is a great thing. I am of the same opinion, to be fair. I'll quote him:

The natural spicery that God gave to these Western Indies is the one called in Castile "pepper of the Indies", and in the Indies, taken the vocabule from the first lands that were conquered is called ají, and in the language of Cuzco is called "uchu", and "chili" in the Mexican one. [...] It is eaten green and dry, ground and whole, in the pot or in stews. It is the main sauce and all the spicery of the Indies [...]

Throughout the different Spanish chroniclers and naturalists, like Oviedo, Acosta, Gómara, Bernardino de Sahagún, you will find concurring opinions on the chili's usefulness, as well as commenting that it is mighty spicy though of very good taste