A good effort.
You start off with a decent riff... it's okay, but it could be better. You build on it with a few more synths as the song progresses... aah, I'm seeing drums now. Here's the tension... Wow! Nice samples there, and cleverly brought in.
Your melody is good - it fits your DnB idea. When you bring the piano in, it felt unnecessary, as if you put it there just because it was a piano. The notes were excellent, but the concept of a piano didn't quite fit. I think, had you found the right sawtooth or something, (maybe a low, distorted-sounding one?) it would have sounded much better. It could have replaced the melody synth you have before the piano, as well... try experimenting sometime.
Your harmonies are nice, but lacking. I hear a lot of low synths, and while it's a good NUMBER of harmonies, since everything was down low the number was in effect cut in half. Try to have variation in octaves, synth choice, etc. It seems you couldn't quite do that.
Your percussion builds up tension nicely in the introduction, no problems there. You have great drum samples and you used them well. You cleverly use them to introduce the melody, but you leave me wanting something a LOT harder and bassier after that buildup. The drums after the buildup didn't justify that buildup, I feel... try to justify your buildups, it makes a song a lot better. ;)
I don't quite get a "behind closed doors" idea from this song... it sounds to me, actually, like a DnB-Industrial mix. I'm not sure what I would have called it, but probably I would have called it something related to a factory, making... something. I'm not entirely sure of that. You set up nice atmosphere and should have built upon it by having bassier drums, more variation in your harmonies, etc.
Overall decent - apparently it's your second attempt at DnB, and for a second one it's decent, I'll give you that. =) Why don't you stop by my audio page and review my latest, After The Nova? Much appreciated, and keep up the good work. =)