As someone who picked up Pit in 3.5 (ouch)
He feels so much better in 3.6
I haven't played a lot of tournaments with him, so I'll give small insight to several matchups I've played, and tell you what I think of it.
Fox
55:45 in Fox's favor.
This matchup isn't terrible for Pit. Onstage requires heavy dash dancing, and most of the percent Pit gets is going to be from grabs. Besides that, he's combo food and upsmash is definitely capable of sealing the deal at 95~ (with no DI)
Pit definitely excels at offstage gimps and edgeguarding, especially since Fox is so easy to punish with a fair or bair. Also, Shinespikes murder an unwary Pit.
Falco
65:35 Falco's Favor
This matchup is hard. Camping Falco isn't an option, and lasers ruin Pit's approach. Also, they can interrupt his Side B recovery, for a relatively simple gimp. Onstage, Pit just gets murdered, and the only salvation Pit really has, is getting Falco with small gimps and a relatively easy upthrow chaingrab that can lead into a bair kill.
Lucario 50:50
I feel that this matchup is relatively even. Lucario is a combo-driven machine, but he's a good weight for Pit to juggle. Also, grabs and arrows work well against him, along with Gimping his recovery. On the other hand, Pit is combo food for Lucario, and considering Nair, Bair, and offstage Aura Bomb, Lucario has several options to get kill Pit, especially out of Upthrow.
Ike
60:40 Pit's favor.
I like this matchup a lot. Arrows are too slow to shutdown Ike's QD options. However, Pit is much faster, has an awesome spot dodge, and can juggle Ike without too much difficulty. Also, Gimping Ike is a lot easier, as Fair or bair will easily beat his Aerial QD, and a lot of the time, Pit can get him too far offstage to recover with just a raw up b. On the other hand, Ike still spaces well with Nair, and can kill Pit with an offstage Fair or Dair. However, due to Pit's speed, I have no problem dealing with Ike.
Marth
60:40 Marth's Favor
I don't like this matchup because tipper. It's the Freddy Krueger of Pit's dreams and basically tells Pit that recovering high is the worst idea he's had. Marth has great combos on Pit. He has good options from grabs, and Ken combos hurt Pit just like everyone else. Pit can win this matchup with good dash dancing and arrow camping. Offstage Marth is dangerous to gimp with fair or bair, but not impossible. He's a pushover when he's directly above you though, due to his limited falling options.
Ivysaur
55:45 Pit's favor
Ivy is easily outcamped by Pit's arrows, onstage, Ivy has better combos and does very well juggling Pit. But because of Ivy's weight and slower air speed, she's way easy for Pit to gimp with a fair or bair.
Pit doesn't do so well with juggling ivy, but his Nair, fair, and dair can get in quickly against any ivy that doesn't have bair ready to hit back.
Also, tether recoveries are relatively easy for Pit to deal with. I usually just drop and bair, and I win.
Samus
60:40 Samus' favor
This matchup is gross and it should take a shower. Basically hell on both sides, as arrow curving and missile canceling both shred. Samus wins the neutral easy. It's arrows are definitely annoying, but he needs to get in to deal the good damage and samus doesn't let that happen so easily. Samus hates up airs, but Samus' dair has priority over Pit's up b, so trading with it turns Pit into a comet, making it hard to kill off the top early
early. Gimping samus is tricky, as Bomb jumping makes her teensy, and she can recovery from ridiculous horizontal distances with tether, but it is possible.
Overall, Samus just has better options and makes it difficult for Pit to kill her.
Sheik
70/30 Sheik's Favor
This matchup is strenuous on my health. Sheik demolishes Pit on the ground. She has chaingrabs, tilts, needles, dsmash, and awesome edgeguard options. Pit has decent juggles on her, and arrow camping is possible if he baits and punishes with grabs, but it's all piecemeal. Sheik can nearly go 0-death without too much hassle.
Falcon
60:40 Falcon's favor.
That damned knee. That fast dash dance. Those long Nairs and uairs. This matchup is difficult. Falcon has the combos, kill moves, and style to kill Pit like a rabid dog fighting a marine. (Filthy Casual pls) Pit 100% relies on getting the gimp on Falcon's recovery. Killing him off the top with Up B is difficult, and definitely not worth the dair Pit would probably eat. Pit has juggles on Falcon and can take him offstage permanently, but he gets very little from grabs, and Falcon can just Nair or fair the arrows away.
Donkey Kong
50:50
Pit has awesome combos. Gimping isn't easy, but it's possible. Kong's bair hurts though, and I don't like the idea of trading with his fair or dair. Pit evens it up with arrows, I think. Simple to just camp DK and force him to make risky approaches.
Diddy Kong
65:35 Diddy's favor
Between the banana, tilts, fair, and side b, Diddy can 0-death Pit. Pit would rely on arrows, up air juggles, and Gimping diddy's up b, but honestly this matchup should be easily in Diddy's favor.
Toon Link
60:40 Toon Link's favor
Pit can play the camp game back at Tink, but Tink just gets better opportunities from it, especially with the AGT his bombs give him, and the different punishes he can get from landing a bomb. Fsmash, grab, fair, etc. Also, Pit doesn't do well against the up b kill, and Toon Link is hard to juggle. His dair beats Pit's Up B. Pit only really excels in chaingrabs and gimps. Tether is easy for Pit to deal with, and any recovery AGT bomb can be stopped with an arrow. Besides that, Pit has nothing in this matchup besides dair->aerial setups
Link
70:30 Link's favor
If there's one character I will absolutely avoid playing against with Pit, it's Link. His zoning tools feel slightly more relevant than Tink's and the arrows don't do a lot to stop him. Juggling is nearly impossible thanks to his dair, and Gimping him offstage shouldn't be hard, but any Link who properly uses his Up b, can basically shut down the possibility for fair or bair gimps.
Also, the ground up b is killer for Pit. Especially out of a grab.
Will continue later, sleep time rn