Greg, I am so glad you liked and implemented my suggestions!! so im gonna press my luck some more and suggest a few more things.
1. Sodium is highly combustible, make it burnable in a boiler for a very high yield (4x of lava simple due to how difficult it is to get sodium) will make heating up boilers easier
2. Beryllium Copper (http://en.wikipedia.org/wiki/Beryllium_copper) a good alloy that has many uses in electronics. I was thinking 3 copper ore + beryllium (it is very rare after all) to yield 20 beryllium copper bars which can be used as a replacement for copper in copper cables and for alternate (cheaper) recipe for copper plating!
3. Palladium - countless industrial uses, can alloy with silver to make electrodes (to be used in forestry as alternate recipe for diamond electron tubes, can be made into special cells that absorb hydrogen (4 palladium + 5 hydrogen) to make extremely potent fuel source that can burn in generators and boilers. Most importantly palladium is not consumed in the process due to its ability to absorb hydrogen and release it.
4. titanium to make advanced machines. 5 titanium (1 in each corner, 1 in middle) and 2 carbon plates 2 advanced alloys as replacement for machine block recipe
5. Liquid nitrogen - already exists in the game already through other mods (not sure which mod adds it) but would be nice to see some integration with your nitrogen cells and ability to pipe liquid nitrogen directly into nuclear reactor as a 1 time outside coolant. Combined with nuclear control you can have an interesting mechanic if reactor overheats pump liquid nitrogen in to super cool it! Of course make it expensive to balance.
Next suggestions involve tungsten (http://en.wikipedia.org/wiki/Wolframium#Alloys)
6. Here is a bit of a weird / cool idea I have. Tungsten + nickel to make kinetic penetrator. Its a round that you fire from some sort of projectile launcher (leave that part up to you). Its a 1 time use projectile that will move forward 30 blocks, penetrating and destroying everything in its path except for bedrock. It would be an excellent tool for hollowing out room or making mine shafts, considering destruction catalyst is gone and tungsten isnt easy to come by.
7. Tungsten + sulfur + manganese to make powerful fluorescent lighting. It will require EU to operate (constant 1eu/t) but will produce very bright light that lights up a wide area + it can have cool graphics. If not too op you can also make it deadly to creepers, preventing them from approaching it!
8. Silicon in advanced circuit recipe. ! silicon plate + 4 redstone to make 2 advanced circuits
And last, but not least I absolutely love chemistry and physics and the fact that gregtech adds so much of it!!! What do you think about a particle collider? Can open up possibilities for synthesizing californium, einsteinium, nobelium, etc. considering we already have fusion reactors it would mix together extremely well. Would need 8k EU/t and you can insert various cells in there to create / break elements!
Thank you very much for consideration, absolutely love the mod and would love some feedback:)