I see 1/2E as American Standard, and 3.0/3.5 as Metric.
1/2E all the basics were different - exp for classes, stat bonuses, that 10% bonus for exceptional stats, etc, etc. You had to constantly flip through six different pages, plus I HATED THAC0. I understood it, but it never made sense.
The non-weapon proficientcies(SP) were a joke a best and more often than not ignored by almost everyone I gamed with. Weapon speed was stupid . . . and the list goes on.
3.0/3.5 is universal, if you have an 17 on ANY stat you have a +3 modifier. You can now have a Dwarven Wizard with no restictions. You aren't penalized for playing a non-human character.
My main complaint with 3.0/3.5 is that there are SOOOO many products coming out that it's hard to keep track of. I don't even go to non WotC stuff any more because there is just so much of it. I really use the reviews on this site to help me buy certain items, just because I don't want to drop XX $$$ on a piece of crap.
I also think we should have a new OT Post: "You know you are trolling when:?"