It's well-known that the PC ports of GTA 3, Vice City, and San Andreas were a shemozzle, thanks in part to re-used code across the trio of games, but also a general lack of care that used to be the norm when it came to PC ports. The excellent SilentPatch has long been the solution, and it's now even better thanks to a significant update that not only fixes leftover bugs, but also restores cut content that was inaccessible thanks to typos in the code.
One big change you'll notice with this version of the patch is that 100 voice lines have been restored to GTA San Andreas. Some of these were only bugged in a specific circumstance—like the lines CJ says when shooting at people, which only worked if you played with a controller. Those lines will now trigger when you pull the trigger when aiming with mouse and keyboard.
A lot of other dialogue that would otherwise never be heard has been restored too. Pedestrians will now have conversations about the weather, criminals have lines specifically for running away, CJ has unique lines for taking over specific neighborhoods and more lines when interacting with sex workers, there are more gang taunts, cops now announce when they have you surrounded or need covering fire, there's a grunt specific to being sprayed with paint, and more shopkeepers have lines for when they're being held up. According to the patch notes, "Most notably, the Ammu-Nation vendor had over fifteen voice lines for this event, all previously unused!"
That's the tip of the iceberg when it comes to improvements across all three games. Lens flares and heat haze now scale with resolution, NPCs can use sniper rifles and RPGs properly, cops no longer shoot gangsta-style, birds spawn correctly, roadblocks face the right way, and you can put a boat in your garage without crashing the game.
Extremely specific bugs, like the one that turned the sky over San Andreas red at 8 pm if it was raining, have finally been squashed, as well as the one that caused an explosion in Fort Carson by incorrectly spawning a plane in someone's driveway. GTA 3's street gangsters now walk in formation instead of meandering around and then freezing, fixing a problem that affected even the PS2 version.
The list goes on. SilentPatch was already essential to fix more blatant issues like broken mouselook, but now it's even better. If you're in the mood for a replay, here are the setup instructions for all three games.

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