The main reason I picked the XBee for this project is that I had one already. That said, I would argue it makes sense even for someone just starting out.

The XBee has a lot going for it: very simple to use, amazing range (the pro has a stated range of 1 km, the normal has a range of 300 meters), no worries about the actual encoding or transmission of data, etc.

Unfortunately, it also has some downsides, including an awkward form factor and relatively high price (OK, $25 for the non-pro model is not *that* much, but you need two of them; then you need to add in the cost of 2mm metric headers and / or a breakout board if you want to use it on a standard breadboard... it all adds up).

This design is modular, and completely link agnostic. The AVR sends out bytes over its serial port, and something (in my case, an XBee) handles the transmission. This could be replaced by a cheap 433MHz transmitter, a serial bluetooth link, or even a wire (although why you would want that, I have no idea...) Of course, what you choose as the transmitter must a) be bi-directional (you could get away without this, but you would want to modify the source code to enable / disable whatever you want at startup, rather than let the receiver configure it on the fly, and this would make it less universal), and b) should be able to run at 3v.