One of the most anticipated features of the new iPhone OS 3.0 has been “tethering,” or the ability to share your iPhone’s 3G Internet connection with your laptop, via Bluetooth or USB.

For web workers — “the great untethered” — iPhone OS 3.0′s tethering represents an opportunity to work with greater freedom, mobility and flexibility. Even for those already using 3G datacards and dongles, the feature means you have one less device to carry. Official tethering has been a long time in coming. Unofficial iPhone apps such as Nullriver’s Netshare and PDANet have provided tethering capability to jailbroken iPhones for some time. Netshare was an official App Store release for a while, until Apple forced its withdrawal due to the lack of tethering rights in AT&T’s terms.

Here in the UK, O2′s tethering support for iPhone launched today, coinciding with the launch of iPhone 3G S. Sadly, despite the fact that O2′s iPhone contracts include “unlimited” data usage, tethering will cost an additional £15-£30 ($25-$50) each month, with no pay-as-you-go option. It’s worth noting that this pricing is identical to O2′s standalone 3G data charges.

O2 is claiming that “using your laptop can be more data-intensive than using your iPhone,” but doesn’t apply the same terms to other contracts and handsets. It’s likely that the carrier simply senses an opportunity to charge iPhone users for something for which they’ve effectively already paid.

In response, enterprising users are already creating patches to tether iPhones to O2 without jailbreaking, albeit running the risk of breaching their contracts as well as disabling MMS and Visual Voicemail. Indeed, even AT&T’s yet-to-be-launched tethering feature is being prised open.

It’ll be interesting to see if O2′s pricing has a negative effect on take-up and usage, diminishing a feature that’s clearly in demand and extraordinarily useful.

Do you plan to take up tethering services for your iPhone…and do you expect to pay?

Related research and analysis from GigaOM Pro:
Subscriber content. Sign up for a free trial.

• Mobile Wrap-up: Q1 2009
• Mobile Q4: All Eyes Were on Android, 4G and the Rising Tablet Tide