the dx11 pack was released just 2 months after the game launched, far from "much later".
the download came in at well over 2GB, so i would hardly refer to it as a simple patch or tacked on download, and it made a world of difference in game. the hi-res pack was nice, but maLDo's pack was far better and really takes the game to a new level.
why go back, you ask? i personally couldn't enjoy crysis 2 until i got a chance to play it with the aforementioned textures pack and dx11. before that, my opinion of the game was similar to yours.
playing it now with all bells and whistles turned on and no HUD command is both a visual spectacle and an immersive gaming experience that i thought i'd never get from this game, but that only occurred because i gave the game a second go after being thoroughly disappointed initially.
i say go back for the visuals alone if nothing else, plus, the game itself isn't half-bad either.
look at this post if you're interested in seeing how much of a difference dx11 plus proper textures make in this game.
http://forums.anandtech.com/showpost.php?p=34404720&postcount=29
i'll have a look but the gameplay won't have changed though.
as for "much later". i had long completed the game by the time that patch came out although i had to use a trainer due to that nano points bug (it reset each time you started the game so couldn't upgrade).
before i look back at C2, i want to (via the other crysis thread) revisit the original with a few mods on.