Progress is slow but steady. If I wasn't such a prefectionist I'm sure I could run through this game pretty easily. But this is one of those rare games where you usually do get rewarded for exploration. Best example I can think of recently... I was poking around a corner of the Farmer's Market and I noticed that a beam had fallen down from the wall. It looked like I could jump to it and it would allow me to walk up and around some of the framing. So I did. The framing led me to a trap door, which opened to reveal two auto-hack tools and three proximity mines! Very rare and powerful items. Stuff like that means that I tend to explore very throughly.
Another thing I'm having fun with is the camera. If you're not familiar with the game; you get a camera and you can use it to take pictures of the enemies. This slowly fills up a bar and when the bar is full you get a hint about the enemy's weakness or a damage bonus, or if you really do it a lot... a new tonic. Taking lots of pictures of the enemies in the Farmer's Market has gotten me a couple of really good tonics.
The best one is basically predator camo. If you stop moving for a couple of seconds, you turn invisible. This is really nice for dodging security cameras. Just wait until it swings away, walk right out into its field of view, stand still, and go invisible. The camera swings back but doesn't see you. So far it seems like this fools everything, provided that you're not actively engaged in combat with them. I managed to piss off a Rosie, and it even allowed me to evade her after I ran away. Another great use was when I came out of the Farmer's Market and Ryan sent three flying bots after me. I just stood still and went invisible... the bots couldn't see me. They flew all around for the full 60 second alarm duration and I just sat there watching them. This tonic also allows you to play evil sniper quite a bit, which of course I love. If you're interested in getting this one, you have to take a lot of pictures of Houdini splicers. Harder than it sounds - those are the teleporting, fireball throwing guys.
I've also gotten a couple of good tonics from thug and leadhead splicers. Static Discharge 2, which gives people a huge shock when they melee you, and Sportboost 2 which makes you swing the wrench a lot faster and run a bit faster. Also found Eve Link 2 lying around, which has been great. I'm almost never out of Eve any more. I got Photographer's Eye 2, but it's sadly limited. With only a 15% bonus it's only barely worth it.
I'm mostly using my ADAM now to buy extra plasmid and tonic slots. I especially need Engineering slots, machines are getting really hard to hack. Safes are starting to have insufficient pieces of pipe available on the board to successfully complete the flow path!
I've found 3 weapon upgrade machines so far. I've used them to increase fire rate on the shotgun, increase damage on the grenade launcher, and increase damage on the pistol. I highly recommend the first two. That last one, not so much... evidently the ammo capacity upgrade is a better choice there. I don't have the crossbow yet, but I have a feeling I'm going to like it a lot. Coupled with my predator camo, it should make for some real fun sniping.