My few observations:
I like Castro. I think he's the real deal. He is hitting his spots and getting hitters to flail at his offspeed pitches that tail away from the zone.
Osuna I'm not convinced as much, and I've felt this way since ST. His control is no where near as pinpoint as Castro, and he's been getting away with mistakes since the start of ST.
I don't know how long it'll be until Osuna gets shelled but I'm not comfortable with him. I still think he needs more seasoning in the minors.
Cecil - I think Cecil can still be good. His breaking ball is still there. His velocity is/wasn't there, but once you get him some more reps and pitching in warm weather I think he will return to his usual self. I don't think he'll see another save until Castro is unavailable for a save game.
Loup - Going back to his outing in Montreal, Loup has been terrible. Control is spotty. I'm not sure if he will be as reliable as the past two seasons.