I still use my MBP quite frequently but I have found that I handle most of my emails via the iPhone.
Browsing (thanks to my poor eyesight) can get tiresome on the iPhone if I do it for very long. I generally need to remove my eyeglasses to read the web page and when I do that, I can't see anything else 😕
All in all, I'm pleased with the iphone's web browser but some sites either by design or because they're buggy don't render as well on the iPhone as on my MBP. For instance, espn, has specific iphone web pages that make the reading better but I get less information and navigation is a lot harder. Other sites that rely heavily on flash fail to come up as well.
In general, its a great tool to surf the web in a pinch but I cannot see using it over my MBP.