And that leads to my major issue with the addon: You require iridium to get iridium.
Then increase the amount of Iridium in the Landscape. (Config)
This is terrible design for a few reasons.
1. You act under the assumption that the player has Buildcraft. While it's a reasonable assumption, your only prerequisites for using the addon are IndustrialCraft, and by extension, Forge. Anything that can't be found in IndustrialCraft needs to independently exist in your mod.
This Addon adds also Automation, so you dont need Buildcrash. (except for Railcraft ofcourse)
while the more powerful devices should require the rare materials. (This is why regular batteries aren't made of diamonds.)
These Devices are ALL powerfull => Need Iridium.
3. That leads to my next point. All of your machines exist on the same level. I see no reason to pick the Fusion Reactor over the Lightning Rod, or vice-versa. I guess my decision would really be based on whether I have more Deuterium/Tritium/Helium cells, or if I have a consistent way of creating lightning. The idea of a Lightning Rod is great, but the effort invested into getting one up and running simply isn't worth it to me, who hasn't seen it in action. An LV, MV, and HV version would go far to encourage me to investiage the technology, as would simpler Fusion Reactors that simply fuse hydrogen into molecular hydrogen, or maybe helium.
Dont worry, Fusionreators are easier to maintain as of a new Feature of V2.06a.
4. Conversely, your Industrial Centrifuge is incredibly easy to obtain. From a design perspective, it's clearly the entry-block into the mod, just as the iron furnace is the entry block to IndustrialCraft. However, all it does it consume my cells and junk materials, and after a really long time, it pops out some other junk materials, and new, strange materials that I have no idea how to use. The only thing I'm really getting out of it are new sources of fuel, but honestly the time they take to make makes them feel more like a novelty, and the fact that there are future uses for them makes me hesitant to use what I have.
If the Centrifuge is "cheap", then you can place more than one. 40% of the Centrufugerecipes were moved to another Device as of V2.06a
5. I've seen somewhat similar complaints to these before, and you wave away the big one, the fact that iridium is so rare, by saying that the rarity is configurable. However, this is a poor argument. Whenever Game Informer, for example, receives a game to review, they play the game on the normal/medium difficulty. The reason for this is that this is the default difficulty, just like the values you set in your config are the default settings. This is the way that you choose to present your mod to the community. Changing it for myself is, to me, cheating. It's no different than me adding items to my inventory via NEI.
Well, Default is supposed to be hard. Otherwise no one would use Hard Mode.
So, my suggestions:
1. Make iridium, not necessarily more common in spawning, but more obtainable. Add different ways to get it. Maybe have a dust that centrifuges into a small amount of iridium dust, a stack of which is compressed to become a single iridium ore. Spending days managing quarries is simply not acceptable, and it becomes all-or-nothing luck.
Try Plantinum Dust. 8 of it make 1 Iridium in the Centrifuge. From which Mod you get it is another Question as I've currently not added it. 
2. Make iridium more visually distinct than the myriad of other light gray ores, and make sure that if it spawns in a chunk, it's visible if possible.
Color can be changed via Texturepack. Iridium spawns everywherein the Overworld, so you should look everywhere to find it. An OV-Scanner can help you much, as its Value for it is 10.
3. Allow your Industrial Centrifuge to be a gateway to additional parts of a mod. In the Matter Fabricator's recipe, the only thing the Industrial Centrifuge does for me is get chrome and aluminum ingots. Meanwhile I have a chest filled with two dozen different by-products that have no use until I get highly advanced machines.
Thats intended or incomplete. Be happy that you have those Resources, when i add more Stuff later.
5. Generally make your mod less soul-crushing. The 'ooh, I want to make that' moment was ripped out of me when I checked what I needed to make a machine.
Lol, thats completly intended. XD
V2.06a:
Added Industrial Electrolyzer, crafted of Extractor, Magnetizer, IC²-Electrolyzer, Tier-IV-Circuitry and Aluminium or Refined Iron
Moved tons of Recipes from the Centriuge to the ~10 times faster Electrolyzer.
Electrolyzer accepts MV btw.
