Technic is the largest and greatest compilation of technical mods in Minecraft, but I feel that the developers need to add a few things with compatibility, preformance, and even some mods.
Technic has around 30 mods, which can take a toll on a less powerful system. I believe that a few mods can be removed. I personally belive that the best example is Mo' Creatures. It can destroy your computer(and reactor) with ease due to the immense calculations this mod requires(and the ogres). When I disabled this, my framerate and lag spike frequency got better. Besides, where does Mo' Creatures even have a place here? Even if you enjoy this mod, it is easy to reinstall it. There are also mods that can be added. A perfect example could be More Pistons. This adds a relevant item and fits Technic really well.
There are also problems with rhe launcher. The big one is that the .exe is broken on Windows XP Media Center Edition and Windows Vista Standard Edition. I do not know about other versions of windows, though. There should also be a default launcher version to avoid a heap of extra files on a computer with low memory and to reduce lag.
These are just a few things that I believe can make Technic the best possible modpack.