Here's some diverse opinions (and some pertinent data) from several professional commentators/journalists:
My originally posted opinion remains unchanged:
If MLB sticks with it, I think I'm going to like this rule.
Initially, the downside is the likelihood of a modest increase in blow-out innings.
On the plus side (at least, for me) I foresee the Increased value, development and use of pitchers who:
consistently perform with better than average command and control
are "rubber-armed" (can throw more pitches per appearance and require less rest between appearances)
are versatile -- starters who can effectively relieve and relievers who can effectively start
have very effective "trick pitches" -- ex: knuckleball
I’m the risk adverse prospect guy, Tony goes with more of who you’d hate to lose from the org, so that definitely favors ceiling.
So you all know I’ve been on Stauffer from the jump. Big Stauffer fan. But the thing about Stauffer is that he’s Kremer with a better changeup, little less curveball without the present command or the stamina to carry a starter’s workload. So while that could be very promising, it also carries lots of relief risk.