My take on what we got and what we gave up.
Jace Peterson--statistics are impressive, but remember he was playing in the California, Texas and Pacific Coast Leagues the past two years. All excellent hitting environments. Similar to players like Pastornicky and La Stella in our systems.
Dustin Peterson--struggled in Low A as a 19 year old. Closest comp in our system might be Connor Lien who had a better season in low A as a 20 year old.
Mallex Smith--had success in both Low A and High A as a 21 year old. Similar to the success that our own Jose Peraza had in High A and AA as a 20 year old. If you consider that Peraza was one level ahead of Smith while a year younger and also playing in tougher hitting environments, you can get a sense of context to evaluate Smith's success in 2014.
It is noteworthy that none of these three made their league's Top 20 prospects in 2014 (using BA's lists).
Collectively, I would value the three at 1.5 WAR.
I will hold off on Fried until the end.
Now for what we gave up.
Justin Upton projects at about a 3.5 WAR player in 2015 while being payed the price of a 2 WAR player. Surplus value is 1.5 WAR.
The draft pick (about #30) is worth about 1.5 WAR.
So what we've given up is worth about 3 WAR.
I saved Fried for last because he is the most difficult to value. I will point out that we got Paul Maholm for Vizcaino (at a time when Viz was recovering from TJ surgery and at a time when Maholm was an effective major league starting pitcher with a reasonable contract with one and half seasons left on it). To make this an even trade you have to value Fried at about 1.5 WAR in terms of surplus value. This is pretty close to where I value him and I would say this comes close to being a fair trade.
I have no problems with this trade. As I have discussed elsewhere, I do have problems with the Heyward and Markakis moves. Those are much more likely to work out poorly for the team.
All the above thoughts are couched in terms of probabilities. In all cases, it is possible a player could end up performing much better or much worse than his central tendencies. But it is not a good idea to base an ex ante evaluation upon outcomes far in the tails of the distribution of possible outcomes.