Clannad: Another World, Kyou Chapter is yet another generic love triangle story that doesn't have much emotional impact unless you are a fan of the franchise. Being a fan of the franchise it felt shallow and underdeveloped; the character depth from the series is lost. This shouldn't have been created, as it adds nothing to the franchise and doesn't do the love triangle thing particularly well.
Still, the animation is downright gorgeous, the backgrounds are wonderful, and some shots are inspired. This does makes what would have otherwise been completely generic and average and makes it at least somewhat worth viewing... but really, a love triangle? Ugh. You can only get away with that if you add in a twist of some sort, of which there is none.
Perhaps it is cynical of me to say this, but Clannad: Another World, Kyou Chapter couldn't have possibly been a worse fit for the series, especially as a bonus to the second season. Now for some spoilers: Tomoya met Kyou (again) as his daughter's kindergarten teacher years after his wife died - had a romance between them started there, it would have had potential to be a touching addendum to the series. Instead, it backtracks from the mature tone of the season it comes from.