This road used to be one of the scariest roads in South America (look at photo) but not anymore. Things have changed. It takes only 3 hours from Banos to Tena. It is better if you choose a sit on the window on the right side. The landscape between Banos and Puyo is really cool (1 hour and 30 minutes approx.) but from Puyo to Tena you will only see vegetation during the journey. In Puyo, buses normally make a small pause (sometimes a very long one of even 45 min) so do not be surprised. You will feel the change of weather from fresh to tropical Humid, very humid, so take a bit of extra water. If you need to use the bathroom, buses normally stop anywhere if you ask nicely.
My favorite option is to rent a bike and go down hill until you get to Puyo, it takes approx. 3 hours but is an amazing experience. You can stop in many spots such as el pailon del diablo, la gabarra, do doggie jumping, or stop anywhere to take pics of the many waterfalls you will see here. Before you rent a bike, be sure to ask if it is possible to leave your bike somewhere in Puyo or not.
Get down in Puyo and from there will take you only 1 hour and 30 min approx. to get to Tena. Going from Tena to Puyo by bike is not a good idea if you are not in good condition because there is not a mountain to go down any more, but a plain green landscape that will take you about another 4 hours.
Eating the hot food that people offer on the buses is sometimes risky, as the temperature of food is difficult to be manipulated correctly when it is sold this way.
The people that serve this food live from these activities and work hard to feed entire families, so if you want support them, it will be better with a few cents than buying their food and being sick for the next few days. You have to be aware that you will be driving on the highway so be careful all the time and respect all traffic signs.