Some people prefer to have their saw on an angle, it allows them to see their work better. As for the angle, just set it to one that best suits you. For me I prefer to have my saw flat on my scrollsaw stand and I use a swivel base bar stool that has a back rest (a yard/garage sale find).
I can picture the benefits of having the saw on an angle, but cant help wonder if you need to always hold onto the timber so that it doesnt slip down the table all the time..