If your yard is well graded and has adequate topsoil and your system is layed out well and it isn't rocky- then doing it yourself might be worth it, maybe.

The only thing hard about seed is keeping it wet- and that part is way easy if you have a sprinkler system.

I had a huge yard and had varying degrees of sod quality- the stuff that wasn't cut exactly even or had dry clumps or tore easily - was a HUGE pain. I was so glad I had a large area that I seeded- sooo much easier. Of course it took a bit more time and if it is on a hill then sod or hydroseed is definitely the way to go.