Cheaper alternatives to Xbee

Is anyone using other radio control module instead of Xbee?

I've been using the nRF24L01(+) modules for a while they work very well with Arduinio. See the URL below for some work in progress libraries.

http://www.madsie.co.uk/arduino/nano-net.html

I found something interesting:

There is written:

Q: How MOD-NRF24Lx interference with Bluetooth® technology, WiFi, ZigBee?
A: MOD-NRF24Lx have 125 channels for communication, some of them are same channels used for Bluetooth, Zigbee and WiFi, so user must implement colision detection and switch through channels until they find free communication channel.

So to sum it up - unlike Xbee that needs at least 2 Modules to make the connection, with Olimex nRF24L01 tranceiver - I can use it on one side (on Arduino board) and for example laptop internal bluetooth on the other side? Am I right??

No what it means is this devices uses the same frequency band as bluetooth which can give disturbance in the signal send and or received.

That's bad.. >:(
When i am going to Xbee platform then i have to buy 2 Xbee modules + 1 Xbee-board for Arduino Nano + 1 Xbee-board for USB to PC connection ?