Hello, Omeletter here. A lot of the things have been said here already, but...
Firstly, I'd like to clear up the speculations about the ingredient yield and how "random" it is. Some wild figures have been thrown about, e.g. 20 snowberries, 15 mountain flowers, etc, etc. Harvest Overhaul was designed to be mainly realistic/immersive - it is meant to simulate the amount of ingredient harvested from the game model, but with a hint of game balance to it. 60% realism, 40% balance is how I'd put it. When making this mod, I looked at the model/size of the ingredient, the plant, and the plant after harvesting. For example, mushrooms come in 3's, so in most cases, you can only get a maximum of 2 (6) or 3 (9) from a cluster, depending on the source it is harvested from. Cotton comes in a small bunch, so you can only get a maximum of 3-4 from a plant as well, rather than 10.
The chances aren't truly "random" as people put it. You wouldn't get 1 ingredient one time, and 12 another. You can download the Excel file with all the minimum-maximum amounts, and also the chances of getting the ingredients at the Optional file section. I decided to simulate the chance of a plant being unsuitable for alchemy, e.g. wilted flowers, by setting up a chance on all the ingredients that the plant can yield but 1 that you get no matter what, so you can't get 0, however that is (probably) bound to change in the next version. Each plant has its own chance - I looked at every plant instead of sticking a 50% chance on them just because. Normally, this results in you getting somewhere around the middle of the possible yield amounts, maybe less, maybe more. You'd be lucky if you got all 12 from a big cluster of mountain flowers.
Yes, it does make alchemy easier so it does change the balance in some small ways. However, the mod does plug in the massive hole that is Skyrim's harvesting system of getting 1 no matter what. At least in this game we actually see the ingredient being harvested, unlike Oblivion or Morrowind. It also allows you to level your alchemy skill without resorting to making extra expensive potions involving Giant's Toes, Wheat, and Butterfly wings that cost around 600 septims at minimum, but have no value if you are actually going to drink them. Like many have said, it's possible to turn the alchemy levelling down by changing a few settings in the uncapper to make this mod balance well with vanilla. Also, numerous people have requested a toned down version which will be provided and the whole mod will undergo balance changes anyway, so this mod may very well be a great addition to STEP's core, although I'm not the one involved with STEP so perhaps the future patches and versions of this mod will tell.
There is also something interesting I found in the CK while making this mod. Each plant has a seasonal % of failure to harvest it. E.g. I can make it so some plants are only harvestable in the summer, and in the winter they only have a 20% chance. I did not bother with that because Skyrim doesn't have seasons - you never see Falkreath being covered in snow and that's a shame, but perhaps this is still a nice thing to put in the mod, maybe for balance or immersion. I'd like your opinions on this.
Dragonborn compatibility - as soon as Dragonborn is on sale, I'll get it. I don't want to play Skyrim anymore, at least for now.
I have also made a small optional addition to this mod called Harvest Overhaul - Creatures. This is merely a few balancing changes regarding animals, e.g. removing money and clutter, and also fixing a few values regarding the amount of claws, tusks, meat, etc you get, so it is actually worth hunting animals for their loot. Although this is not a massive, in depth mod - I'd love to have the ability to kill a deer and butcher it, taking everything; bones, different cuts of meat, antlers, hide, etc. this is a nice fix to make hunting feel better, more useful, more profitable. That is a great addition to STEP's core, if it doesn't have mods that do so already.