You'll find that the cost of GPS is wrapped up in the maps you use. If you subscribe to the AT&T $10 a month product, the maps you'd use will not be installed on your Pocket PC. You will use online maps and the use of the maps is dependent on an ongoing data connection - so you'll also need to be sure to subscribe to AT&T's data plan (probably an unlimited plan if you'll be using it a lot).
You can also purchase GPS software that includes an application and the maps. You'll install the maps, probably to your storage card, and, other than the cost of purchasing the software, the use of GPS will be free.
I don't know about the tilt, but when I purchased my hw6925, there was a 60 day demo of GPS software included with it. After 60 days I had to buy the software or some other software to continue using navigational software on my pocket pc.
Here's a link to an article I wrote about GPS - mainly in regards to the hw6925, but you may find it interesting too:
From my pocket to yours....: Basic GPS