My main problem is that every tutorial and example of XBee temp networking I can find, and there are many, configures the XBees in API mode. I assume this is because Rob Faludi used a temp network to demo API mode in his excellent "Building Wireless Sensor Networks" book.
But API mode is not only beyond my abilities of comprehension at this moment, it also appears to be something of an overkill for a project which, for the time being consists of relatively simple communications.
It was easy enough to figure out how to get the various sensor nodes to read and transmit the temperature values. And the new Arduino IDE has a pretty straight forward "transmit to Pachube" sketch. I figure just using an Uno and Ethernet Shield should be the simplest base station set-up for now. Unless such a set-up is beyond its capabilities. In such a case, I have a number of other options available includinga MegaADK
One last thing. Terry King has a cool example of using the Cosm library somewhere on this board. If you haven't seen it yet, do a quick search and take a look. It may simplify the work even more.