I haven't tethered my mobile phone with my netbook for Internet access for quite some time now for a number of reasons. One of them is that in the countries I usually stay, cheap prepaid options for a couple of hundred megabytes or gigabytes per month are available in the 10 to 20 euro price range. As a result I usually buy a SIM card that I then only use with a 3G dongle. With roaming prices capped in Europe I then mostly use my home SIM card for telephony and small screen web browsing.
But leaving that scenario asside, tethering is still worth at least 120 euros a year (based on 10 euros a month) if you can use the data contract with your phone/smartphone SIM instead of buying a separate 3G dongle and prepaid/contract SIM with it. I'm sure that still appeals to many people.
One of my 'must haves' from a mobile device in this regard is Linux/Ubuntu support for tethering. To my delight, even the latest Nokia models such as the N8 are still detected as 'modems' in Ubuntu (10.04 Lucid in my case) without any need for additional drivers. Very good!
I have noticed that espeically Android phones are used under windows as "virtual network card" but I never tried them under Ubuntu. Has anybody tried that and can leave some feedback here as to if/how that works?