1. Jetpack flame renders behind clouds, nether portal, etc: http://prntscr.com/7zi83g
2. Energy upgrades can be inserted into electrolytic separator and you can build an infinity energy source.
3. All basic blocks can be blaced through the player: http://prntscr.com/7zibly
4. Machine sounds still glitch when hearer teleports.

Some improvements:

1. Against ru_RU.lang fix: http://pastebin.com/4svAKs2f
2. Better plastic textures: https://www.dropbox.com/s/zpuppfpty1smby0/plastic.zip?dl=1

Some ideas:

1. Add randomly moving trajectory for baloons.
2. Create multiple creative tabs. For example:

• Mekanism: Basic
• Mekanism: Tools and armor
• Mekanism: Plastic blocks

New plastic textures added, thanks!

2- Energy upgrades in the seperator does not decrease energy usage. Only energy capacity.

Which version are you on ?

I know that its hapens on some graphical cards and fixing by manipulating GL_LIGHTING in render.

Also, this is very very terrible: http://prntscr.com/7zlxoh

2- as @ruifung said, Energy Upgrades don't decrease energy usage. They only give it more of a buffer.
3- This is a vanilla issue last I knew. I can't remember if it truly is, but typically I've noticed that even on vanilla servers. This cannot be fixed by a mod.

RAWRwins254 and ruifung are right on parts 2 and 3, and I'm not sure there's any easy fix to part 1 - vanilla particle renders face the same issue. I'll take a look at the sound issue later, I'm pretty sure it's already reported. I'll implement your fixes when I have a chance :)