1-2 wasn't a big deal for us. My 1st was a little over 3, he was potty-trained, weaned, slept through the night and was old enough to know to stay close when we were out and about. Also, since newborns sleep so much, I was able to spend a lot of focused time with him still, read to him, color pictures and such. He also has a very sweet temperament.
Now 2-3 was a haze for like 6 months for me. My 2nd was only 19 months old, she was not potty-trained or weaned and things were really hard for a while after my third was born.
3-4 has also been super hard as my second is still having potty issues and my 3rd is not potty trained or weaned. My 3rd just turned 2.
So I guess I think what makes it more difficult is how close the spacing is.
No matter what though, it is not so hard that I would change it, the joys exceed the challenges and I love my life and each of my children like crazy. So even if may look like a disheveled little mess, rush around like a psycho, and never sleep more than 5 hours in a night, I have 4 wonderful children who I get to hang out with and witness them grow into the people they are going to be.