The changes in bikes at your price level since the '80s are not much, although advertisers would like you to believe otherwise. If you want to pay lots more you can get the exotic materials mentioned by sluggo, and lighter does really mean faster on uphills and in stop-and-go situations.
If you pick bikes that are equal in terms of inflation-adjusted price, 80s bikes and modern bikes are pretty similar in terms of speed/usefulness/convenience.