My mum just bought one of these, easy enough to set up for her in a few minutes.
The IP address is:
http://192.168.10.253
You can find the IP address of it when you connect it directly with the cable, by opening a DOS prompt (type CMD and press Enter after clicking the Start button) then type IPCONFIG and make a note of the Default Gateway and type that in to your address bar at the top of your browser (Internet Explorer / Firefox / Chrome).
Username:
admin
password:
1234
It picked up my mum's wifi and extended it. She was using a borrowed Sky extender, but since they're going for between £20 and £40+ on eBay, I can't blame my mate for wanting it back!
I've plugged it in to the mains behind her Sony telly and connected it with the same LAN lead that I set it up with. Hopefully that'll save her £90 on a Sony wifi dongle for the telly - not that there's much "Smart" stuff to see I expect.