If my husband is away for more than a night or two, I miss his presence, so don't sleep well. Flipside, without him there, I can nest the pillows whatever way I need to prop whatever body parts need it to deal with aching muscles and discomforts.
When he's home, I have to put up with occasional snoring. If his face is pointed my direction and we're close, he sometimes puffs air in my face when he's asleep (he sleeps like a log). This does disturb my sleep, because it's a cold puff of air, and I normally don't like cold air in my face. He also tends to sleep with arms up by his head, so if he's restless, I can get an elbow in the face or a fist (never been injured from him yet). The other night when he was sleeping like that, he was restless and nearly thumbed my eye. He also is a spinner and may put his pillow at the foot of the bed, so I may get kicked in the face. He also in his sleep piles the blankets on me, trying to take care of me. This is sometimes a problem if I'm already too warm and have already pushed the blankets off.
When he's sleeping deeply and isn't restless, it's no problem at all.
That all sounds awful, but it's not as big an issue for me as electronic sounds, a breeze that's too cool, itty bitty lights from the electronics (the computer, all its devices, the TV/satellite box/DVD player, etc.), street sounds, daughter's cat pawing at the door to open it so he can shove his head through the blinds to look out our windows or plowing over us as he rushes from one window to another or chase after an imaginary prey, or my own aches and pains. These are the main environmental things that make sleep difficult. I sleep so shallow, that I notice everything when I sleep.
I don't think these things cause my sleep problems. I've had 3 sleep studies showing I "arouse" 139 times in an hour and only levels 1, 2 and REM sleep, 0% delta sleep, but they can't diagnose what is causing it. No apnea, no RLS, no narcolepsy, etc.
Environment and partner do contribute, but are not the cause for me.