I just finished a project using these exact same parts! After looking at the high prices on the XBee chips I got a few of these same transmitters and receivers from Sparkfun to build a remote control for one of my robots. The chips have a lot of quirks but are not very hard to figure out despite some comments to the contrary on Sparkfun. If you are interested in Arduino I would highly recommend Tom Igoe's book Making Things Talk. The book is filled with a ton of wireless projects and walks you through the Arduino basics. If you are in L.A. and interested in Arduino I recommend checking out the occasional Arduino classes offered at Machine Project (www.machineproject.com).