This tweet from megnut is the best summary of what the latest iPhone can now be:
“Yes, iPhone = my computer, and $399 is worth it. Haven’t bought new laptop since late 06 and don’t plan to for long time.”
The iPod Touch is pretty much the same as the iPhone, except with the phone taken out. And, crucially for me, no mobile data connection available pretty much wherever you go. So, much as I like the iTouch, it won't just yet become my "new laptop". (Wherever you can get onto a wireless network, you're OK. For example, at the wedding last weekend, the hotel handily had free WiFi for all guests, and it was doing a reasonable job as a stand-in computer. But WiFi is still not available in many places you want internet access.)