As in using extra totems/spells/equipment/programs introduced in books like "Cyberpirates" and "Awakened Lands?"

The systems are entirely different. It'd be like using a d20 book to supplement V:tM.

(Well, not really. But the idea is similar.)

Settings details (aka roleplay 'fluff') from previous Shadowrun titles is all still good.

Game mechanics (aka rules 'crunch') will probably need to be adapted, sometimes heavily so.

Even the setting details will largely need changing. Most of the Matrix stuff is flat-out invalid now, and everything else is at least 7-10 years behind the times.

It depends on what you want to do. If you want to use the "missions" those would work wth tweaking of the NPCs/Creatures & any gear/matrix stuff. The overall storyline still works.

As for gear, you will have to convert (and use your best guestimate on) the old to the new system. Can be done but will take some work.

I use some of the stuff from SR3 in my SR4 campaigns.

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I pick and choose from all supplements for my campaign, so I'd say yes for fluff. Crunch seems to need more work to convert.

Really? You can pick any five year period from 2050 to 2065 (No, hell... You can pick any five year period IRL from 1989 to today) and there will be a considerable amount of things that will be significantly different. I fail to see how relevant setting stuff will be in 2070 aside from (most) places not moving on maps.

I don't really follow the "canon" timeline and events too closely. Some events I skip entirely, others I drastcially change or shorten (Renraku arcology shutdown was finished in 1 to 2 weeks, f.e.). When exactly the Fuchi breakdown and corp war happened is not really important for my campaign, just whether the runners got involved in it or not.

basically, each new supplement book I decide what to implement of it in my game, and how - either by running the events detailed in the campaign, dropping them as "won't ever happen", saving them for future runs "someday", or just adding them as "happened already" in the background.

So far I avoided Surge completely, dropped most if not all from year of the comet, and changed a lot of the rest. I kept corp war events.

As an example for altering stuff: The Renraku arcology was taken over by some mad AI, UCAS forces and Renraku troops took 1 to 2 weeks to solve the issue with brute force - spec force secured the reactors, then it was just a matter of time until the AI ran out of ressources, time and space confronted with a military operation supported by a megacorp. It provided me with a window for a run or two inside - Competing megacorps hiring runners to secure some paydata and information from inside during the confusion - but keeping the arcology in deus' hands for longer than this would have been silly in my campaign, and not serve any game purpose either.

So, I'd say one can easily pick and choose from all supplements.

There is nearly no such thing as a useless suppliment, regardless of the system. It just makes more work for the GM in the form of conversion.

Want to use a full-conversion cyborg from the Chromebook as a CZ? You're the GM.

Even many D&D modules can be played in SR with a little rewriting, especially if they are city adventures.

Town watch... Lonestar... samesame.

What about old spells and totems? Are they already in SR4? And what about programs? I want to be able to black hammer somebody.

So? One out of... How many million important changes?

The point is: Every sourcebook is important in its own way. Each one sets the stage at the time of its release.

News from 1905-1910 and 1995-2000 are incredibly different. The supposed Y2K bug, for instance, wasn't even thought of in 1910. And we all know how big of a news item that was in 2000.