Whoaaaaaaa this sure is a thread.
Boots give vertical flight and chest give horizontal flight. Use both together for proper flight.
Er, this is incorrect. Jetpack without flight control currently has 2 'modes': straight up, and up+forward. up+forward splits your thrust evenly between the two directions. Jetboots and jetpack simply sum their thrust and cost values for a total thrust/cost per tick of use. So the 'ideal' is probably just to install both, unless you're using Flight Control.
Eh, I'd prefer to have one uber tool, and one uber weapon rather than one item that does it all. For one, power consumption would be less. For another, it is my spinal reflex to switch from my drill to my chainsaw when I hear that all-too familiar hissing sound behind me.
One of the problems I had with the major mods in 1.2.5 was the insane number of tools and clutter in my inventory, especially the ones that HAD to be on your hotbar, like the EE2 rings. I would prioritize IC2 power tools, even though I should have probably used machines, just to save on inventory slots. So my focus is on making it possible to use a single tool to cover as wide a range of capabilities as can be done.
I definitely feel your pain on the 'accidentally destroying my projects while fighting off mobs', though - what I personally do is set all the tools to a key (should be possible if you're using the current recommended or later) and then press that key in my 'panic' when addressing a creeper.
Alternatively, if this just doesn't suit you, you can make 2 powertools and colour them differently so you can tell them apart