Good work ITead! I believe you just built an R/2R ladder. There are integrated chips that have all the resistors already laid out as the way you soldered. I've asked a similar question, here's the post:
http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1275426082
Richard gave me a link to an R/2R ladder sold at mouser.com
Give it a try if you want to make your circuit more compact!