It depends a bit on which wireless router it is, and on what you want to do.
If you have one PC, connected directly to your broadband, and that's all you want - then the router isn't much use. You could always sell it on eBay...
If you want to use your broadband with more than one PC, and especially if one of them is a laptop (or a palmtop etc) then the wireless router can be very useful indeed. I have one here, and various family members use it when they come visiting with their wireless-enabled laptops.
You will want to know what security features it has. Running a wireless access point with no security is probably OK in a house out in the country, but not a good idea in a block of flats.