Ah, really? What power bump would that be? I have to admit don't remember anything of the kind.
Depends. If you went from AD&D to 2E and missed Unearthed Arcana, the first thing you'd notice was weapon specialisation.
However, soon after 2E came out, there were a bunch of Complete * books, which occasionally had some delightfully broken combinations.
When I went from AD&D + UA to core 2E, I admittedly didn't see a big power bonus. But the bonus that UA or basic 2E gave to fighters was a major power-up. (An additional +1 to hit, +2 to damage and +1/2 attack per round? Scary!)
Cheers!