They got rid of Otis, the camera, and improved the A.I., all things I wished were worked on.
I don't mind the saving system, forces me to learn the the layout and the overall quickest paths in the game.
Time limit I'm fine with as well. As Frybird there mentions, it get old right quickly if you are just killing zombies (Zombie Genocide proved that right away for me in the first game) with no real push to move onward.
Plus with a time limit, you get what most games haven't had in a while. A chance to learn, practice at, and eventually do a perfect run through accomplishing everything in the least amount of time. Not something for everyone to try, much like speed runs in general or getting 100% of a map/collecting every orb thing, but for those of us who want it's a great incentive.
The story is focused on time, play Case Zero and see that, which wouldn't be as effective otherwise without it. Yes Resident Evil and Silent Hill don't have it, but they don't need it with their mostly linear story paths.
There are plenty of open world games to play with no time limit, you can explore to your heart's content, and kill a bunch of mindless enemies with completion of the story at your own pace. If Dead Rising's system isn't for you, well plenty of similar titles you can enjoy and a few others with cheat mode that will come close. Hulk: Ultimate Destruction is a fun hidden gem.