I'm excited to play her. Even more excited to see who else they bring over. In theory we could see a few Overwatch heroes in a row as the game goes into Open Beta/soft launch in a little over a month.
If I had to make my own Overwatch tier list of who would be the most unique ("S" tier) moving all the way down to the most similar to what we already have for Blizzard to go off of when implementing new heroes (ie: they would develop S tier first, then move down the line):
S Tier
Tracer (obvious, totally unique compared to anything else we have)
Winston (leap, like a "4" range with his electrocute, dropping the shield to help your team would be bonkers)
Mei (ice wall, brehs. So good. And freezing people, dat reverse ice block)
Junkrat (traps, plus positioning tricks with the concussion blast, plus a different kind of ranged weapon)
Symmetra (turrets on a support + shields only + a teleporter...dunno how they implement the teleporting, but it'd be neat to see)
A Tier
Hanzo (ranged bow hero like others but should have the highest range along with Raynor, etc, not sure how they would tackle his wall-climbing mobility, ult would look great in HOTS)
D.Va (really only has two skills, the ult/use of the mech would make this either super fun or super terrible)
Zarya (has Gazlowe's ult, but the ability to put a small shield on yourself and others coupled with the laser + concussion blast would make her pretty unique. Ranged tank, more or less.)
Genji (plays very much like Zeratul, except no stealth and can redirect damage + has solid range)
Lucio (similar healing to Kharazim, just without the stacking, and he's ranged and can provide speed boost)
Fun Tier
Pharah (kind of like Tychus' Odin the hero, but can fly)
Zenyatta (heals just like Morales, but can also boost damage and does very good ranged damage which would be fun)
McCree (Raylan Givens from Justified)
Too-similar Tier
Widowmaker (Nova)
Torbjorn (Gazlowe)
Roadhog (Stitches)
Bastion (not quite a 1-for-1, but Sgt. Hammer)
Soldier 76 (any number of heroes, but as Milly79 says, Raynor most appropriate)
Reaper (Valla)
Mercy (Lt. Morales)