Should I hold on to the Galaxy 3 or should I get the Galaxy 4?
There will be ROMs based off of the S4's system that will bring some of the new software features to the S3. The S3 is also supposed to get a lot of them via OTA anyway, but who knows how long that will take. This is a great video Wicked posted over at our sister site, Samsung Galaxy S4 Forum, comparing the two with regard to day to day usage and features - it should answer a lot of your questions, but it will boil down to how important some of the improvements are to you:
I won't be!!
Still love my GS3. People are AMAZED at how customized it is. In fact a lot of people can't use it because they accidentally open things or move to another page or something. And when iPhone users see all the widgets I have, and realize they have to go into settings or open an app to do the same thing....the way they try to hide the jealousy...it's great...
Point being I have absolutely no reason to upgrade unless I want to feel cool with the latest and greatest. I've done this a lot in the past and what I've learned is.....it's not worth it. Wait about 4-5 months for initial reviews/problems/fixes. You might find the S4 is just a flashier S3. Sure NOW it sounds way more advanced, but the X2 was supposed to blow the X out of the water.
Yeah, that didn't happen...
I think the IR blaster is one of the coolest things, and if I could afford it I would get it just for that. No more handling sketchy hotel remotes, or yelling at the kids when they hide my home remote. The screen will be awesome I am sure, but i would be surprised if it really makes much of a difference on such a small screen. There really just isn't much that the S3 is lacking, and I wont upgrade till Bid Red forces me out of my unlimited plan. But props to those that can always have the newest super-phone.
I have to respectfully dis-agree. The SGS4 has a full 1080 HD display, 13 MP Camera, and a Quad-core processor. Thats a pretty dramatic improvement in my humble opinion.
I got both the Droid DNA and Note 2 when they came out. There is a VERY noticable difference between the 1080 display on the DNA, and the lower res Note 2. It's surprisingly noticeable.