I don't know about the lunar trainer, but I train regularly in the Lunaracer, and it's one of the best shoes I've ever worn in my opinion. The exception is that it isn't good for speedwork, like mile pace stuff or faster. It is too soft to be great for sprinting (though I do it sometimes anyway).
I have also experienced very little of the "wearing down" effect changing what the shoe feels like. Many of the rubber nubs on the bottom have worn off (though they reinforced these in the Lunaracer II), but it doesn't feel like the structure has broken down like I've felt with normal trainers.
Some people (I think more than most think) don't need "support," so it can be a great shoe despite having a flexible last and a uniform sole material.
So, yeah, unresponsive, but comfortable, light, and great cusion while still very flexible. In my opinion, the lunaracer is definitely worth a try.
For what it's worth, I train mostly in lightweight shoes (currently cycle through lunaracer, gel speedstar, and new balance 757), I run 70-100 miles per week, and I haven't been injured in years, part of which I attribute to the switch to lighter, less "supportive" shoes. Knock on wood.