polyester is strong stuff. it is next to impossible to hand stitch it, so machine projects are really necessary, and use a good new needle. the ones for knits...ball points, sharps actually snag on the threads sometimes, and cut them.
my mother just gave me a box with partially peiced polyester lone stars...they are fairly old, and the seams seem to be holding up very well, there does not seem to be alot of fraying. it does look as if they used about a 1/2" seam instead of 1/4" that is about the only difference i can see in construction technique used on these.
make a practice block mixing fabrics and working with them a bit and see how you like them and what you come up with. I would think poly would be good for bags and stuff because it holds up so well, but that is just me.