Some analysis from Crawford Boxes site:
Michael Foltynewicz
Michael "Folty" Foltynewicz (pronounced "FOAL-ta-NEV-itch") is easily the headline name in this deal. The #57 prospect in baseball, according to MLB.com, Folty made headlines for his triple-digit fastball, which he pairs with a nice changeup and a still-developing curveball.
Folty made his MLB debut in the bullpen in 2014, throwing 18.2 innings with a 4.09 ERA and a 16.7% strikeout rate. His minor league strikeout rates have been consistently good - nearly a batter an inning in Oklahoma City in 2014 - but control problems have plagued him for his entire career.
Foltynewicz looked to be a solid contender for the Astros' 2015 rotation, as he's considered largely major league-ready, though some still believe he may ultimately find a home as a late-inning reliever, where his fastball velocity will play up.
Rio Ruiz
Ruiz was the most highly-touted Astros third base prospect after being drafted in the fourth round in 2012 - that is, until the acquisitions of Colin Moran and J.D. Davis in 2014. In Lancaster (a very offense-friendly environment) in 2014, Ruiz continued to show his trademark plate discpline and hitting ability, including his power potential, while playing a very good third base.
However, concerns have surfaced among some of my scouting contacts about his inability to go the other way. He's been a slow burner over his career - he missed most of his senior season in high school with a blood clot and got off to a slow start in professional baseball - but he's put together a nice career, even earning an invite to the Arizona Fall League in 2014, where he slashed just .187/.292/.227.
He's very much a ceiling prospect in a system with two options - Moran and Ruiz - who may have made him dispensable. But he's still a few months away from his twenty-first birthday and could already be ready for the high minors. That's no small accomplishment.
Andrew Thurman
Thurman, the Friday-night starter at UC Irvine, was drafted in the second round in 2013. An inning-eating build, a mid-nineties fastball, and two good breaking pitches had fans anxious to watch his development. Still, it surprised some to see him remain in Single-A ball all season in 2014, where he accrued a 5.38 ERA over 115 innings.
Like the other two prospects en route to Atlanta, Thurman has the potential to be a very solid player, but in a system teeming with C and C+ pitching prospects, he failed to separate himself from the pack. The 6'3" righty is the least-flashy name in the trade, and yet could end up being the crown of it, when all is said and done.
Analysis
Losing Foltynewicz, Ruiz, and Thurman is a blow to the Astros' system, without a doubt, but not necessarily a crippling one. It immediately gives the Braves one major league-ready flamethrower in Folty, plus a very promising young infield prospect and an innings-eater type in Thurman, who could steadily move up in their system, and may even land in their top twenty preseason prospects list.
For the Astros, a glut of pitching depth in the minors absorbs the impact of the loss of Thurman and Foltynewicz, though the latter's impact on the 2015 roster will almost certainly be felt. Ruiz may be the hardest loss, as he's developed a strong following among prospectphiles, and for good reason.