The route is interesting if you want to see Chachapoyas and continue your tour further north to Ecuador.
The tour can be done in 2 days, with a stop in San Ignacio. Although often described differently, the problem is not the transport in Peru, as there is constant traffic of collectivos.
1. Chachapoyas-Bagua Grande (day 1)
type: Collectivo (shared taxi)
price: 22 Soles
duration: 3 hours
remark: Currently (07/07) the road to Bagua Grande is under construction, which is why it is closed from 7a.m. - some time at night.
Because of that you have to leave early (between 5a.m. and 6a.m.) from Chachapoyas. But no problem: there are plenty of Collectivos at this time because of the road situation.
2. Bagua Grande-Jaén (day 1)
type: Collectivo (shared taxi)
price: 7 Soles
duration: 1 hour
remark: The first Collectivo drops you at the place where Collectivos leave for Jaén. If not, take a Motocarro (1 Sol) to the 'parrada'.
3. Jaén-San Ignacio (day 1)
type: mini bus
price: 10 Soles
duration: approx. 3.5 hours
remark: mini busses from the terminal in Jaén are very organized! Unusally enough: they sell you a specific seat and they are only stopping for people on the road if there are seats available.
4. San Ignacio-La Balsa (day 2)
type: collectivo (shared taxi)
price: 10-12 Soles
duration: min. 2 hours
remark: La Balsa is the border crossing to Ecuador. On the ecuadorian side there are only 2 possibilities to continue to Zumba at 12.30 p.m. and 5.30 p.m. As you have to get one of those busses you must leave early from San Ignacio. Keep in mind that the collectivo just starts, when it is full. If you're late there might not be enough people. Consider to pay for the missing passengers in that case, as the "fallback option" in Ecuador is more expensive.
If you miss one of the busses mentioned above you can hire a camioneta for $20.
5. Zumba-Vilcabamba (day 2)
duration: 5-6 hours
remark: busses leave from the center in Zumba at 4p.m. and 5p.m.
The road is a terrible dirt track (_very_ bumpy)
If you time it correctly, you can go from Vilcabamba to Chachapoyas in as little as two days of NON-CONTINOUS travel. I assume you can take the same route either direction. For purpose of this tip, I will give you the information from the direction I traveled: Vilcabamba to Chachapoyas. Now, it's been a while so excuse the lack of town names in areas of Peru. Basically, you start by taking the bus out of Vilcabamba to Zumba. You'll probably arrive late in the afternoon in Zumba so you'll have to spend the night and catch the first bus to the border at "La Balsa." From there, you can catch a "collectivo" (shared taxi or if you're lucky a small mini-van bus) to the next town, which is San Ignacio I believe. From there it gets tricky. Your best bet to reach Chachapoyas will be a series of one-hour collectivos through several towns in the region. Just ask the locals for help and they will guide you the rest of the way. I managed to do this in 2 days, but I believe it can be done faster now... see, back in 2001, there were no bridges connecting the two border posts. I had to take a balsa boat to cross the river :). By the time you reach the border they may have finished building the bridge crossing the river. Hence, there may be a direct bus rather then taking all the collectivos.