Yep, finding my way through the gun mods at the moment. I just picked up a bad-ass sniper rifle from the enemy camp, taking up a huge chunk of my inventory. So now I have two, a silenced one and a cooler-looking one. Hard to find ammo for them though. In fact, the scarcity of ammo plus limited inventory space has made me do takedowns more often than shooting.

I just noticed about the energy cells as well... you can be patient and just use that one energy cell, and once a cell is empty, it doesn't recharge unless you eat something. So that extra cells is just for when you need to takedown two or more enemies quick. That multiple-opponent-per-takedown aug sounds cool but really, how often can you sneak up on two guys?

Really contemplating on the hacking augs though; I've "passed" so many terminals now that are security 2 or 3 or even higher and I'm annoyed I cannot hack them even though I am not the hacker type.

I have pretty much the same approach to the game. Upgrades for hacking, especially early in the game, are critical and upgrading the inventory is also important since I like to carry several different types of weapons and accessories. I also like to upgrade the number of power cells since having multiple power cells allows you to take down several guys before your energy depletes.

I'm embarassed to say that I died a few times because I tried to take down a second or third guy without realizing that I had used all of my power cells. Doh!

Or that the second guy was a little too far away for the multiple take down augment. LOL
The first time through I only used the Typhoon a couple of times. This time I'm gathering all ammo I can for it and plan to use it. At full power it can take out pretty much anything, and you only have to carry ammo.

The first time, I put all weapon mods on the assault rifle. This time I'm using the pistol as primary. Ammo is easy to come by and it's powerful when built up. I carry that, the assault rifle and the silenced sniper. I wish the crossbow and dart guns were more useale, but with being so large and with the scarce ammo, they just aren't worth it. I'd love to play this game without having to keep up with an inventory system and unlimited ammo, just to go all out stealth weapons for a change.

In my experience: quite often. In fact, that was one of the first augmentation I've picked on my second play through.

We were wondering about the energy cells first as well (I'm playing this game also on the PS3 together with a friend). But I guess the game would become far too easy if the energy cells would all completely recharge automatically. So far, I have only upgraded to faster recharging, which in my opinion is already enough for most parts of the game- if you don't use energy-hungry augmentations such as invisibility. There's however one particular part where quickly taking down all enemies is crucial and the additional energy cells really become helpful.

On my first play through I was still carrying lethal guns with me for taking out the bosses. But now, on my second play through on PC (aiming for the Pacifist trophy), I don't care for them anymore. Bosses I take out with grenades and mines and the only gun I take with me is the tranquilizer gun, which comes in handy in a few situations. For most of the time I simply knock enemies out though.

I'm planning to upgrade the Typhoon though for taking down at least one of the bosses. Don't know if it's worth it but I really like the animation.

I bought HR + the DLCs, but I still haven't tried it out. I've been preoccupied with the Civ 5 Gods and Kings expansion.