I've had an iPad 3 since it came out, and I bought the iPad mini the day it came out. I just replaced my iPad 3 with an iPad 4. The reason was that the 3 was just a 16GB WiFi version and the iPad 4 I got is 64GB with WifI and Cellular. I kept having to swap things in and out of the iPad 3 and lately I was having some issues getting connected at places with WiFi. So I went ahead and splurged on the iPad 4. Yes I know I could have waited for the 5, but I didn't want to wait anymore. The iPad 4 is twice as fast as the 3 was and the camera is better, which I don't care since I don't use the iPad cameras that much anyway. My life will be made simpler just because of the more memory and the addition of the Cellular.
That being said though, there are times and places I prefer to use the mini, which is also a 64GB model, but WiFi only. There are times I prefer to use the larger iPad. Since they both now have the same memory, I could essentially have the same items on both rather than having certain programs on one or the other. But like I said there were times when I didn't feel like carrying the larger iPad, so just carried the smaller one. and vice versa. With the one having only been 16GB, there were apps on the mini that I could only use on the mini, and there were a few apps I felt better suited for the larger iPad.
As for the endless debate over retina vs non-retina, the iPad 3 was retina and the iPad mini is not. For what I needed to do I really didn't notice any difference in the screens. Both screens looked amazing in my opinion. If I looked super close at each screen, sure, I may have noticed the dreaded pixelation, but trying to find such a beast would just lead to my getting a headache or even a migraine so why should I bother.
For me the decision was merely to replace what I currently had with something that would make my life easier overall. As long as it works I'm OK with the decision I made. Since Apple hasn't even announced the iPad 5 yet, it could be a matter of weeks or even months before it is released. For me I needed a better solution in the here and now. I didn't need something that may or may not have certain features somewhere down the line. When the time comes that those specs are announced and a release date given I will, at that time decide if it was worth it or not. Right now the iPad 4 fills my needs perfectly and that is what matters the most.