He has been decent for sure and the good news it appears he's added a pitch and improved the movement of another so there's a possibility the improvements (though I doubt he's going to keep a 2.88 ERA or anywhere close to that) could be for real.
He added a slider to go along with his cutter, curveball, changeup and 4-seamer and although he's only thrown it 44 times, it has been his best WHIFF pitch at 32% and batters have put up just a .104 WOBA off the pitch so far.
He completely remade his curveball adding almost 8 inches of verticle movement and five inches of horizontal movement. So instead of a rolling curveball he's got sharper break and less of a 12-6 movement to more of a 1-7 movement. Surprisngly it's been less effective than last year in the early going.
The changeup has the same well below average movement but batters have put just a .208 WOBA vs a .337 WOBA last year so perhaps he's plaing it better.
At the end of the day, the slider seems to be a good pitch for him and it will be interesting to see if that becomes a pitch that helps his below average fast ball and changeup play up a bit.
It's still not a great package overall and batters hit him hard, and his 5.14 FIP is probably closer to his talent level at best. Saying that, he could end up being a long guy/bulk reliever.