We visited in July 2008 on a staff retreat with all the Lao WCS protected area staff. We were in meetings all day so just did walks 7-9am and two spotlighting trips (one in the rain). We saw lots of gibbons and hornbills and sambar deer, muntjac, civet (small indian and common palm), slow loris, otters, blue-bearded bee-eater, flying lizards, pig-tailed macaque, black giant squirrel, ground and arborial squirrel. We also walked in fresh elephant tracks and saw a large cat scratch on a sambar (probably tiger - no definite record of leopard as far as I know).

So it was great to see, but a pity about the insensitive nature of development in the park. Huge cleared areas around infrastructure. Great for breeding up deer, but in a national park? And also the river was very polluted with sewage, plastic bags, etc.. And the tiger die-off from introduced domestic pig disease...

If you're stopping over in Thailand it's well worth a visit. Much nicer than Bangkok!