[heresy]

Were you running old versions of iOS? Personal Hotspot has been in it since March, seems odd that iPhone users would not be running at least 4.3 by now.

[zzzmarcus]

If you're in the US, that feature will cost you another $240/yr unless you're already on the 4gb data plan.

[mikeash]

You can add and remove it on a month to month basis, though, if you only need it intermittently. In any case it's well worth the cost if you do need it, and is much cheaper than other ways of obtaining cellular Internet access.