I have my GS3 for three days now, love the phone, so snappy! But like OP, I do missed a few things from the HTC Evo I had for two years.
I missed the HTC Task and To Do List widget. I downloaded a few similar app from Play store, but it is not as good as the HTC ones in my opinion, missed these so much.
I also don't like the way Gallery was set up, I can't scroll to the end of a Gallery (maybe I just don't know how). I have folders with up to 2000+ pictures, so without the scroll, it takes some time for me to scroll to the end of the folder.
I don't like the stock calendar and e-mail app. I don't like the layout of the calendar app, but I guess I'll get used to it. For the e-mail, I just switch to the yahoo email app instead, but I missed the HTC email app, where I can have all my yahoo and hotmail email together. And easier to switch from one account to the next.
With all the above said, I still love my new GS3!