to actually answer some of your questions. speed depends on which version. .11a is 54Mbps, .11b is 11Mbps, .11g is 54Mbps (compatible with .11a and .11b).

you don't HAVE to subscribe to use it. if you have a wireless router at home you can use it. and there's a food court by my work that supplies a hotspot for free.

i believe battery life shouldn't be too bad compared to something not using wireless, but that depends on signal strength and how much you transfer.