I used it when doing my father's lawn, he bought it and insisted I use it on his hills. Although we were fortunate to not have any hard or long rains, I imagine it might add some protection from a very breaf cloudburst. But I can't say that I saw any difference in germination rate between the covered and uncovered areas. I did find it a real PITA when trying to determine if the seed under it was staying moist during germination.

Dchall - My fall reno of my front yard I did exactly that, rented a water fillable roller and rolled it good after seeding. But, I also lightly covered in straw.

And the straw vs hay thing is funny. I know very clearly the difference, but have seen posts here and had discussions with people that apparently don't lol ..I couldn't imagine covering a fresh lawn in hay.

Grass - Thanks. I think I'll stick to my straw. I realized the amount on craigslist isn't enough anyways and I'm not gonna go out of my way to get the stuff.

Here's some information on a product we use called Blue Yellow Seed Mats. We have used it to grow and maintain turfgrass on difficult slopes. It is a fabric with grass seed and fertilizer woven into the fabric.

http://grounds-mag.com/productaward/seed_category_winner/

There are far too many people who do not know the difference between hay and straw.

Another common mixup, almost happened to me during my last visit to the feed store. I asked for alfalfa thinking only about bagged rabbit pellets. What they rang up was a bale of alfalfa hay. Fortunately we caught that at the register. I should know better by now.

I also have a slope that needs erosion control. I am planning on using straw blanket material, such as this: http://www.strawblanket.com/prod01.htm

Straw has long been used as a soil stabilizer when seeding turfgrass. One major problem with lawn seeding is having a heavy downpour before the seed is well rooted. I have seen a downpour wash away 1/2 inch of topsoil (and all ungerminated seed) in 5 minutes in a lawn seeded 6 days earlier. Straw mulched area in heavier flow area 50' away was not disturbed.
Also, a hundred years ago, wheat was also sown in a fall seeded cool season grass planting. The wheat would germinate almost instantly, and have a web of 6" roots within a week. How's that for quick soil stability? The wheat, being a cool season annual, would just die out next summer. Unfortunately, economics even influenced life 100 years ago, and wheat was dropped to save money in seeding turf.
Reuseable seed blanket sounds great, but when will you reuse it? LOL! Properly planted turfgrass seed will germinate at rate listed on seed container, no matter what you use as a mulch or cover. The covering does not affect actual germination one iota. It helps to retain moisture and prevent erosion. Mulch with straw, leaving about 1/2 of soil visible thru straw, about one bale of straw per 1000 sqft. Leave straw after germination; it will decay in a few months. Removal will damage new seedlings. If you have some wheat plants from poorly threshed straw, you have a free bonus.

I have a sloped front yard that I lost all seed and topdressing to hurricane rains last year. Plus I have dogs who race and dig in the back yard. This year I'm putting down Curlex I quickgrass, a biodegradable mat. comes 4', 8', 12' wide I think x 100'. This mat is designed for erosion control.