If you expected something broken (which is justified since HL loves dropping overpowered characters) you shouldn't get too excited. DSH is not broken at all, and definitely not overpowered compared to some other challengers. He's in the middle of balanced and really good.

Doom Spears

Definitely underwhelming. They don't travel far at all, and they are pretty slow too. You can outrun them with a simple dash pad. The upgrades for it give you duration which makes it a little bit better, but the travel speed of it still makes this ability a downright trash ability most of the time. Pretty situational.

Doom Wings

Not much to say about this one. It does give you flight and the super form theme for shadow, which is kick-ass, and also pierces shields. Doesn't deal damage though, just knocks them up. Pretty cool boost, but there's far better boosts going around.
The upgrades aren't too bad. They increase your speed.

Doom Blast

The double slash effect might give you shadow glazers dopamine, but this ability isn't that great in terms of utility.
The damage is fine. Problem is that the hitbox is.. kinda buggy? I tested it out with my friend and it sometimes hits behind you. Add lag and delay onto that and this ability becomes a messy carousel.
The speed boost is fine. You can get double pick up with the upgrades and spam it down to beat most supers.

For conclusion, Doom Shadow is definitely a force to be reckoned with- just kind of underwhelming. I didn't talk too much about the good stuff his abilities has to offer, but those moments are up to you to live and learn.

He's fun.

Opinions on DSH based on experience so far (5k - 6k)