
Although it's essentially the same, in upgrading it to "N" Apple have introduced a bit more functionality to the unit at the same time. Whilst tinkering with it, I've found something very useful - something which you can't do with the old "G" revision.
I've had a few problems with the wifi reception around my house - quite a few dead spots, and patchy signal strength - so I'm now using the Airport Express to boost things up a bit. It's widely publicised that the Express can lock onto the wifi signal from an Apple base station and then relay it to extend the coverage, but I don't have an Apple base station. I've configured it slightly differently.
I've taken an ethernet cable out of my existing Netgear wifi router (which is still on main wifi duties), and plugged this into the ethernet port of the Airport Express in another part of the house. Using the Airport Utility on my Mac, I've then set it up to rebroadcast the signal it's getting via it's inbuilt transmitter. All quite mundane so far - but the clever bit (as far as I'm concerned) is that the Express can use the same SSID as the existing network, so your client wifi devices only see one single network name in the list of available networks. Your wifi device - laptop, iPod Touch, phone, whatever - will use the strongest signal in any given place, and switch if necessary, all completely seamlessly.
I've now got a decent, strong signal virtually everywhere in the house - a clever solution from a VERY versatile Apple gadget!
If you want to know specifics about the setup, just ask in the comments.