Short answer: yes.
Long answer: yes, but it's manageable. Ness loves to pressure with PK Fire and juggle with PK Thunder, yet he'll seldom, if ever, use PK Flash and may use PSI Magnet to nullify our arrows. What's really dangerous about the PSI Prodigy are his standard attacks, particularly the following few.
- F-smash - THIS CAN REFLECT. If timed correctly, he'll smack our arrows right back at us. This isn't all that useful against Pit, since our arrows are fast and easily spammed, but it's good to know regardless. It's also a pretty strong f-smash as standard.
- D-smash - Ness's unsung hero of his diverse and creative moveset. What's so interesting about this move is that it goes backwards: whereas most d-smashes go forward -> back, Ness's goes back -> forward, which can and will catch you off-guard if you aren't watching what he's doing. Even if he whiffs the first hit, chances are the second hit will sweep up under your feet and catch you for a clean hit. Be sure to shield / spotdodge the second hit, if nothing else.
- Dash - Simple but effective, it's a multi-hit attack and comes out quickly. You can just shield it, but it strings together with ease and can rack up damage if you're not savvy.
- U-tilt - Juggling tool. Doesn't do much damage and won't launch, but it can do to keep you in the air so he can follow up with PK Thunder or f-air.
- F-air - We all know this one. Can be comboed into out of d-throw multiple times and can push you off-stage if you're too close to the blastzone.
- D-throw - Does decent damage and, most dangerously, leads into a lot of combo possibilities. Try to keep him at bay so he doesn't grab you.
- B-throw - The infamous kill move itself. It's just a ridiculously strong launch, and because it's a grab, there's not much you can do to escape it. Just don't get caught in the first place. He can also follow up with PK Thunder and f-air from this if you aren't killed by it, so be prepared to mix-up your landings to keep him guessing and counter-strike the wee fella.
Ness has a varied toolkit and is great at pressuring and zoning. PK Fire in particular is dangerous, since even if you shield it, it leaves you open to be grabbed, and the Orbitars are too slow to be used against such a spammable move reliably. He can also hit you with PK Thunder from afar, though he is wide open when he uses it, and if you can get in quickly enough, that's a free hit or grab for you.
I'm honestly not too sure how to beat Ness either. I'm familiar enough with his moveset and his tricks - now I just need to learn how to counter his moves and catch him! >w<;;