Are the cheap $150 stands good? YES!
Is there a cheaper alternative? YES! I use two light stands with a 9 foot piece of 3/4" galvanized pipe between them. Run the pipe through the seamless, then add a couple of 90 degree elbows and attach to the top of your light stands. It's a cheaper solution and the best part is you'll have two light stands which can be used for other purposes when you're not shooting against the seamless.
Colors? I'll have to agree that white & black are the most useful. Only other color I use a lot is "Sky Blue." I use the Sky Blue when I shoot a model in my studio and use Photoshop to knock out the background and make her look like she's outside.
: Use 2" wide packing tape to tape all the edges of your seamless paper before you use it. This trick will help keep the paper from tearing as you use it. Some of my seamless is over 20 years old and still in good shape.
Since seamless paper is two sided, extend it's usefulness by painting the backside. In the example below, I spray painted light clouds on my blue seamless.