On first glance, I like this trade. While DeSclafani is a classic "#5 starter" who is a 50-50 bet to implode midseason, it was important to add depth there and they didn't have to pay the full $12M or full with Seattle sending money back. Though if I had to bet, I'd put money on him not making it to the end of the year in the rotation.
Just looking at Topa's stats from last year, I am a fan. I have been clamoring for more bullpen additions and this is a quality addition. I've looked through his game logs and I'm really impressed, he wasn't just hid in the 5th-7th inning, he pitched in quite a few high leverage situations (23 holds and 3 saves). In 75 appearances he only gave up a run in 12 of them and multiple runs in just 6. He should be able to fill Pagan's role that was left open. Who knows if he'll be any good next year since he is a reliever who doesn't rely on strikeouts, but I still approve.
I am very surprised we got a top 10 prospect and a borderline Top 100 one to boot. Gonzalez throttled level A at age 19, then struggled when promoted against competition far older than him. With our farm looking somewhat questionable in depth, it's nice to have an addition - not to mention another piece to move for an MLB player if needed.
Bowen appears to be mostly a throw-in, being a 12th round pick who had a decent first year at level A but will already be 23. Maybe he can become a reliever at some point but I don't expect to see him make it to the majors.
Overall, seems like a quality trade that opens a full-time position for Julien to play (and Farmer makes more sense at his salary as the full-time utility INF). As much as I have enjoyed Polanco as a Twin, his health has become a problem and his fielding isn't what it once was. I wish him luck in Seattle.