We purchased one on the 1st, and everyone here is still using it. I love it for winter here, and I'm down a few pounds.
We do have the luxury of another bedroom, so space isn't a big issue with it. We have it set up in front of a big window with a cd player and television. I'm enjoying lots of books on tape and the rest of the fam prefer to get a little tv time in.
If the place were cramped it might bug me or I'd take it downstairs to the basement. Honestly, I was unsure we would use, but my kids aren't little (no safety worry) and the weather here is just not walking or running weather year round. That said, I do like getting on the treadmill for short stress relieving burst or just catching 15 minutes of exercise here and there throughout the day.
My dh is a runner and will always use it when the weather is bad, but he prefers running outside. When he really runs on this one, we can hear it downstairs, but if someone is walking or jogging it isn't noisy.
I think a good one can be a blessing if you use. A good one can be a little expensive and does take up a lot of room, we have a space saver one that folds up.