If you have a s60 phone which has wifi you can also use joikuspot
http://www.joikuspot.com/
I use this on my N78 and it seems to get more reliable connections than bluetooth and it definitely seems to be snappier.
I also use ATT $15 a month unlimited 3G on the phone and have not been charged anything for tethering and such.
( it sucks battery power dead in about 3-4 hours so I also carry a charger)