I really appreciate the obvious tension between Guzma and Kukui, as well as the obvious inward tension Guzma seems to possess. He's a pretty good translation from the games to the anime, which isn't always done effectively — and I especially liked Ash's reaction to his arrival. I don't think I've seen him that serious since the beginning of the SM anime, so it's good to see him show a little more gravity.
I think Guzma's going to be a good rival in general — we haven't seen a full battle between him and Ash, not between him and Kukui, so it'll be interesting to see his full team and whether it resembles his game team. Given the lack of full teams in the anime, having Guzma compete in the league to prove his worth both to himself and to Kukui would make for an interesting turn. I know his plan is to destroy it, but I also like the idea of him aiming to destroy it by winning and dismantling the entire system while champion.
I definitely wish he wasn't so late in the arc since I love his character, but he's not a disappointment. I think he's worth the wait.