Warning - this is full of spoilers!
These are among the first adventures I owned, purchased as G1-3.
I first ran these in elementary school. The last time I ran them, I ran G1 and G2 for my high school gaming group. They consisted of an Unearthed Arcana-era party - a Paladin, a half-elf Ranger/Druid, a Magic User, and a Fighter. They had some henchmen and followers (mostly, the Paladin did) but I don't recall many details.
They quickly trashed G1, which is very front-loaded with encounters. Destroying the hill giant chief and the best and most effective of his followers is something you can do pretty quickly if you don't mess around or outsmart yourself. After that, as deep as the module is, nothing left there is a true challenge to a well-armed circa-9th level party. I don't recall any of the groups finding the hidden spooky stuff in the basement, but I do recall lots of poking around and fighting everything. By the time you get to the rebel orcs, I found my players couldn't care who side they were on, and fought them equally.
G2 took a little longer, and featured a short appearance by a second Paladin (the player didn't stick around). My most vivid memories are of this part of the series. Every group that went through had a big fight with a remorhaz, too, but none recovered the best treasures thanks to liberal use of fire spells. Everyone fought the various special visitors, had lots of fun fighting two dragons at once (although I recall they died quickly, and the scribbled out HP tallies in my copy make it seem that way too.) I clearly dramatically changed the loot in some places, too, putting in a quest item as part of the dragon hoard instead of some other loot, a Doss Lute (I think we had a bard at one point), and some others. I also remember that this is where my friend TR's fighter Tomas deCon picked up his Shield +1, +4 vs. Missiles.
G3 I think I ran once. In high school we finished G2 and I had something really exciting ahead, and no interest in running D1-3 and Q1 (especially since two of our players were in the original elementary school group that cleared D1-2 and Q1.) So we just skipped G3 and moved on as I recall, moving on to the campaign climax war and castle storming (where, unrelated to G1-3, they fought and killed an arch-devil.) In my earlier running, I recall no one trusting Obmi or the prisoners they freed, either, and that it took a few delves. I remember an epic fight near the bottom of the entrance to level 3 and notes that suggest a lot of survivors made it there. But I also remember that, like G1, the main leadership was found and killed right away. No one bothered with the evil temple, either. I don't even remember people going in it. The big melee in the entrance room backed by everything, countered by the party unleashing everything they had, and that was that except for smacking down some more drow and moving on.
The drow I don't recall being especially badass once the giants went down and they ran low on spells. They have some cool magic items, but lots of them are "hit as 3 HD monsters" and if the PCs are all negative AC, that means they mostly miss while the PCs kill them. Which is what I recall happening, actually. Still, evil elves were fun back in the day, before they became the entire basis of the gaming ecosystem.
One thing I do remember is fights took a while. PCs got missed fairly often by the giants, but suffered lots of damage when they were hit. Giants, on the other hand, got hit often by high-level PCs but when we played pre-Unearthed Arcana/pre-weapon specialization, cutting down a 50 HP giant could take 3+ rounds even for a high level fighter hitting for high damage. With weapon specialization, the giants died faster but still took a lot of killing.
I also remember that this was the only module we ran where people got Wishes as treasures - there are a few, scattered around.
Speaking of war stories, you can also some of Delta's war stories, although he ran them with customized OD&D, not AD&D, so it's a bit different. The guys at Roll For Initiative talk G1, too, down to room numbers and descriptions - no war stories, though.