So I almost never used Chems in Fallout games. I hated getting addicted and then being forced to either find more of the drug or get it cured, and often the drugs had visual distortion effects (particularly when they wore off). And in general I dislike short-duration buffs from consumables.

That said, in Fallout 4, I might consider becoming a chem-head --- although if I were to use chems more extensively, I would likely take any chem-resistance and chem-duration-boosting perks.

Some chems have obvious combat effects: Jet boosts Action Points, Med X gives protection from damage --- or rather, you ignore it --- and Psycho increases your damage, although how it increases the damage of your guns I cannot imagine. Buffout increases strength, and hence carrying capacity and melee damage in Fallout-4, likely. Was never really clear about Steady, Hydra, Turbo, Rebound (?) and some other chems.

There is one chem whose effects are less clear in Fallout-4.... Mentats. In previous games, Mentats would give you a bonus to PER and INT, if memory serves (need to pop some Mentats!). In previous games this let you detect foes at farther distance (meh) and more importantly it indirectly increased your PER and INT based skills like hacking and lockpicking.

In Fallout-4, however, there is no lockpicking or hacking ~skill~ as we understand it now.... just perks, either you have it or you don't. So when you pop a Mentat, what effect ~is~ there, really? Does it just boost your Hacking / Lockpicking perk up one rank temporarily? That's a pretty substantial boost over their previous effects. In previous games getting +5 PER would get you, like, what, 5 more skill points? Ten? But jumping an entire perk-rank in Fallout-4 would be the equivalent of jumping 25 skill points.

Boosting INT/PER (or STR with Buffout) should also allow us to access dialog options that are gated by SPECIAL stat requirements, but will not, of course, allow us to choose perks that have SPECIAL requirements higher than our base.

If Mentats work like I suspect, however, it might be worth carrying some around in order to get, essentially, two free perk ranks (Lockpicking / Hacking) whenever you want/need them.

I suspect that they only boost perception and inteligence, of course thats still quite a benefit, especially if ya use vats alot and/or want to boost your exp gain.

With artificial strawberry flavor?

I remember there was a computer log where a science station got defunded when they found out the personell weren't scientists, and were just abusing Mentats.

Your assumption that Lockpicking and Hacking (or any other activity) will not be effected by these Chems is premature..... Not enough is known about the details of the skill / perk system yet. I know the extensive speculation on the details have been discussed to death, and lots of posters have just blindly accepted some of the speculation as known facts, but they are simply an educated guess based on VERY little actual information we have available.

I find it difficult to believe that those Chems that gave skill boosts in previous games (via temp SPECIAL increases) will be rendered useless by the new system.

And even then if the perks are pretty dang useful, you never know when you'll be in a situation where you NEED that little boost. A hit of Jet for that extra bit of damage soak. The extra brain power from a mentat to work over that terminal or the odd abandoned but functional robot drone.

Kind of like in fantasy games, there's always the consummable "potion of elemental defense". I never use these, but I know that, you never know when you're gonna come up on something that really hurts with it's fireballs and a little Fire Protection will come in handy.

More tools for the trade are always welcome.

Which game? I feel the need to find this now.

...oh hell where was it...

I think it was a terminal found in Old World Blues.

..or was it Fallout 3...

I can remember having SO MANY MENTATS (especially after raiding Mobius' stock) in New Vegas that it was insane. I wanted to have a lot so that I would never have to deal with withdrawal but I wound up just gathering lots and lots and never using them. There's probably a lesson there. Like don't delay gratification till after your dead. Or maybe: use your drugs immediately kids.