The promotion is obviously deserved: Bryant was hitting .355/.458/.702 with 22 homers, 43 walks, and 77 strikeouts in 248 at-bats over 68 games for the Smokies. He was leading the Southern League in OPS with a 1.160 mark, a full 164 points higher than his nearest competitor. His rate stats were stellar (wRC+ 219, wOBA+146). He's played reasonably well on defense, good enough to project that he can stay at third base.
The only flaw I can find is an elevated strikeout rate; 25.9% is higher than I'd like to see in a perfect world, although frankly that is nitpicking, given his high walk rate and outstanding overall production. There was clearly nothing left for him to learn in Double-A.
There's been some questioning among Cubs fans and Bryant fantasy owners about Chicago's timing, why it took so long to move him up to Iowa given his dominance of the Southern League.
Personally I do not have a problem with the decision to give him a half-season in Tennessee. Christian Villanueva, the incumbent third baseman at Iowa, is not having a good year but proved himself in Double-A last year and deserved a full shot in the PCL. I also think it is better to move a prospect too slowly than too quickly, so I don't have an issue with Bryant "paying his dues" so to speak. It isn't like they were keeping him down in Low-A.
What happens now? It's fashionable to disparage Triple-A competition and to advocate skipping prospects past that level. However, philosophically I think most prospects benefit from a good exposure to Triple-A.
You tend to see better fastballs and younger, more physically-talented pitchers in Double-A. In Triple-A you see older pitchers, many with major league experience, who may not throw as hard but have better command and more refined secondary pitches. Even elite hitting prospects don't always adapt easily to that: Bryant's teammate Javier Baez is a great example. He murdered Double-A last year but has been much less effective in Triple-A, exposing flaws that will need to be corrected before he's ready for the majors.
Now it's time to see what Bryant can do with the same challenge.