Almost perfect experience
We ordered Hang Tien Endeavor 2 days 1 night trip directly through the website.
Trip was quite great having a campsite in the jungle. People very friendly with only one speaking English. Everything well and securely organised.
8km trekking in the jungle and 5,5km in caves was quite enough for me, but not for my fitness-freak wife. Remember that most of the time it's uphill and downhill through quite dense flora, in high temperature and humidity, in long clothes.
Don't expect to see much of wildlife. We saw nothing. Not that it is a problem.
By swimming in the Hang Ruc cave they actually mean that you have to swim your way through (in a kapok).
There was a little friction regarding information provided on WWW, by e-mail and PDF. For example we were asked to bring headlights, but they actually provided us with them.
We were told that a vegan will be provided with local fruits (having in particular a watermelon and bananas in mind), but only bananas were provided in limited amount. We were surprised on the way back that a guide insisted to pay for watermelons from a merchant on the road.