Avenger, I placed an order for 180 ft. of 2.2 mm Zing-It with http://www.wesspur.com. The cost was $30.62, $27 for the rope and $3.62 USPS first class shipping. That beat the http://www.treestuff.com price of $34.22 ($25.95 plus $8.27 UPS ground). I'll PM you once I receive it.
I read a lot of positive comments about treestuff.com. However, if choosing between 17 cents per ft. and 19 cents per ft, I'll choose 17 cents a foot. We'll see how long it takes to get to me and the whole post-purchase customer satisfaction.
Got mine through WesSpur as well. They had it to me within a couple of days, if I remember correctly.