For me, it really depends on the project. Like with the denim quilt it was smooth sailing until I got to layering it together and quilting it and with the gigantic Wind Waker sea map wall hanging its just about everything that needs to be done before I actually work on it (designing, sizing, techniques to use, etc.)
But I think something that's always going to be something I'm going to hate is the layering it all together part. Don't have much space to work with so getting it all together is Hell. I used the wall to get the denim quilt together. Quilting it is not that fun either. Well, with smaller projects its easy, but there's not much clearence between my needle and the body of my machine so it gets harder to quilt larger things. I've learned if I'm working on larger things and I need to quilt in the middle I have to tightly roll up what's not being quilted at the moment and then try to run it through the machine. Looked like I was sewing a huge blue carpet roll when I was quilting the middle of the denim quilt. lol.