I'm switching my bikes over to IGH as I go...I have 2 Rohloffs, 1 Alfine and 2 Nexus 8 IGHs. Ideally you'd use a bike with horizontal dropouts or an eccentric BB to tighten the chain without using a tensioner. That gives you the most benefits of the IGH in terms of minimal maintenance and highest reliability. Having said that one of my Rohloff bikes uses the Rohloff tensioner and it works fine - has needed no attention in a couple years.

Don't worry about loss of efficiency or weight with a Rohloff or Alfine/Nexus 8 - it's simply not an issue. It's far more important what tires you are running if your concerned about max efficiency. I never ride one of my IGH bikes and even think about the hub gears vs. derailleurs. I also still have a few derailleur bikes so I get to switch back and forth regularly for comparison purposes. I'd always rather be on an IGH bike.