Very seamless! I have used MiWi in the past and it just killed my battery. I love having it integrated within iOS because you can tell they really optimized it for the phone and it is hardly effecting my battery life.
The power to turn your phone into a Hotspot is incredible and although jail breaking is an option, I love not having to worry about all the problems that come with jailbreaking.
Thanks.
I recently dropped my unlimited iPhone plan to the 2GB plan for a $5/month savings.
Then, when my current month iPad plan is up, see about exchanging the $30/month I pay for the tethering option. Or just the $15/month plan.
When I bought the iPad, there was no official tethering, and there was no WiFi available at my work I could use for lunchtime use. Now there is. So less of a need for an iPad 3G plan.