To me, there are only two drawbacks to sublimation and with some creativity, you can easily overcome them in your decorating business. Those 2 restrictions are the lack of white ink in the process and the fact that sublimation ink only transfers and bonds to polyester.
The lack of white ink means that the best shirt for sublimation is going to be a white shirt so you have a good base to put colors on. A white shirt will not affect the look of those colors. If I'm printing a blue image onto a yellow shirt, the blue image is going to end up green on yellow. If you have nice white, puffy clouds in your image and you print it on to a light blue shirt, those clouds are going to be light blue puffy clouds. This means I can't really create black shirts, but there are some ways. If I print black ink onto a red shirt, that will work, but yellow onto that same red shirt will barely show up. The only way around it is to start with a white shirt and imprint the entire front and back, and many people do that onto shirt panels and then sew them together after decorating.
The second restriction is the ink doesn't transfer into the molecules of cotton as the inks only transfer to polyester. For example, if you are decorating a 50/50 shirt, it only bonds to the polyester portion, and it might actually look somewhat decent on that first print. However, after it gets washed for the first time, that ink that's just sitting on the top of the cotton is going to wash out. The ink will never wash out of the polyester side, so if I'm doing 100% polyester shirt, it's going to look the same after one wash or after a thousand washes. The more polyester content you have in the garment that you're printing onto, the better your image is going to be with more pop and more vibrancy.
There are some papers being sold out on the marketplace that claim to be sublimation onto cotton. While they are becoming better and better each time I have tested them, my disclaimer is that is not true sublimation. You're still sticking something on top and you're not actually making it part of the cotton.
Thanks to Printwear Magazine for the question.