Never found a use for it beyond the spear users in Undead Burg (and it was easier to riposte them than kick + attack 2-3 hits anyway). After the first area of the game, it was never useful ever again.
In Dark souls 1, enemies took extra damage when in a stagger animation. The kick caused them to stagger, so it's basically the same thing as Dark Souls 2's shield break minus the animation. After being kicked, the enemies in the Burg are 1-shot by most if not all weapons.
You say it wasn't useful after the first area in the game, but the only reason for that is because there weren't many shielded units past the first area in the game. If the same were true for Dark Souls 2, the shield break would be equally useless.
I prefer the kick because A) while the kick will result in additional damage if it successfully shield breaks, it's not quite as overpowered, B) the animation is faster, making it easier to pull off, and C) it doesn't bring fights to a grinding halt waiting for all the animations to finish. The only disadvantage is that rather than being a 100% guaranteed shield break if it connects, it's basically a static -stamina attack, so if the enemy/player has a ton of stamina, it's not going to shield break. That could easily be tweaked for this game though.
Also, the shield break move in Dark Souls 2 looks ridiculous.