Alrighty... after playing a couple of Endless Mode games on my 4th gen... the game does run a LOT better. There are still some small hiccups, especially when there's loads of dinosaurs on the screen... but it's definitely playable. Managed to get a 140 chain goin before screwin up on my first game... which is surprising for me, especially on the smaller screen (I'm use to playing this on my iPad... and not having to carefully watch where I put the edge of my finger to pick out green guys from the red...) - but yes... definitely a HUGE improvement from the last version.
Thank you so much PikPok!!!