Yeah it downloads map for the route you need. Which is a nominal cost depending on your providers datarates. But it's no more than browsing to something like google maps via wap.
I've yet to use it in anger but it directed me to the chipshop and back the other night
You can download without the GPS and have a look by browsing to
www.nav4all.com/install it'll give you some rubbish about being free until August 2006 which isn't true as on the website it says till 2008.
I'm only going to be using for the odd journey here and there so perfect for me. Defo worth a punt for the cost of a GPS reciever which you can sell on at a profit on Ebay if you don't like it

the one I bought from Mobile fun I've seen sell on ebay for about a fiver more than I paid if you include delivery costs. So win win