The 'old way' is exactly how I traveled Vietnam. My and my friends didn't have any plans at all, all we had booked was our first night's accommodation in Saigon. The rest we planned from talking to people at hostels, we ended up with a big group of about a dozen of us by the time we got to Hanoi.

In my opinion, it's the only way to travel.

I have never understood planning in advance your entire holiday down to the hour. I guess it's more important if you're American and only get 2 weeks of holiday a year.