After having executed the following commands:
adb reboot bootloader
fastboot flash recovery /path/to/recovery.img
Instead of executing "fastboot reboot", simply disconnect the USB cable and remove the battery for a while. After having reinserted the battery, power it on in the typical recovery fashion (holding down the "volume down" button and pushing the power button until the device begin its boot process, do not release the "volume down" button before you have entered CWM recovery) and you should enter CWM recovery.
EDIT: Apparently, you'll only be able to access CWM recovery on this sole instance. In any further attempts you would simply land at FTM ("volume down") or Android recovery ("volume up" or "adb reboot recovery"). If you want to enter CWM recovery again, you're going to have to redo the flashing process and remove the battery, as explained earlier in this post. Such is at least the case for me.
Edited by konpa, 14 February 2013 - 03:22 PM.