To be more specific, Pikachu's playstyle is pressuring, which is somewhere between rushdown and bait and punish. If you're fine with that, what matchups in particular do you think you'd use Pikachu for?
NAKAT and many others use Pikachu as a secondary and they do well. So you should be fine too.
Most people can agree that Pikachu's worst matchups are Mario and Ness, which are both somewhere around 40:60.
After that, there's many varying opinions. Mr. Game & Watch is often listed as a slightly bad matchup, at 45:65--about half of the Pikachu players I've talked to say this. Some people also argue that Fox, Doctor Mario, Yoshi, Luigi, and Meta Knight are at least slightly disadvantaged, but I've only heard these from a minority of Pikachu players.
I hope this helped.