It depends on how much water you used--the starch will be more concentrated if you used less water. It also depends on the type of pasta you were cooking. Ones w/more surface area will give up more starch. Regardless, I always save out a bit of the water to add back in along w/the sauce. The water will boil out, and the starch lends a creamy/smooth mouthfeel to the sauce. Nice:look:
No problem, Ninja_59 To really take it over the top, add either a splash of heavy cream, olive oil or some softened butter and stir everything together madly. You'll end up emulsifying the fat into the sauce w/the starch as a binder. It will be Ridiculously Good. Make sure to do it on high heat--finishing should take no more than 1-2 minutes so you don't end up overcooking the pasta.
Adding the pasta water to your sauce to 'finish' off the dish has a lot of benefits.
When pasta comes out of the water, and use a lot when cooking it, it's like a sponge in effect as all that dry starch on the surface of the cooked pasta wants to suck something up so by adding it to your sauce, along with a ladle or two of water (depends on the amount of pasta you're using), it allows you to up the heat a bit and let all those flavors come together as one.
It also does a great job of keeping your past 'hot' when bringing it to the table. Every good Italian cook and chef I know finishes it off like this.
Jfield, I also like your suggestion with the butter and a little cream... I've used cream before but most times when I make a bolognese or vodka sauce.