We visited Nature Nirvana few weeks ago. In summary, I will not visit again. They have nice location, food is alright, service okay. What kills all the fun is the access. The road from Chikmagalur is just horrible, and the fact that we went there during rainy season made it worse.
In case someone needs directions - take Baba Budangiri Road out of chikmagalur, proceed 7km where you need to take left at the fork. Continue on this one for some 15-20km. There is a bit of steep climb, and down. You pass Attigundi (sp?). Then you see a turn off with Nature nirvana sign on the left. Next 7km is nightmarish dirt road.
Almost everyone in our group got leeches - that was another turn-off for any serious hiking. In contrast - it may be little more expensive - but I have really enjoyed our visits to Jungle lodges including one in the same region - at Bhadra.