I was talking to an enthusiastic NaNo-er and they found the deadlines an encouragement. They wrote shedloads and had finished their 50,000 words about five days ahead of schedule. Good for them - it's a huge achievement.
Others won't have made it. To them I offer sympathy. When I tried NaNo last year it completely did for me. The deadlines were a stress too far. I felt guilty in parts I didn't know I could feel guilty about. I stopped writing.
Different strokes for different folks, horses for courses. But, word counts aside, we can learn a lot about our writing process from the experience. My speedy NaNo-er discovered that there was more time available for writing than she'd previously thought. I discovered I don't like additional deadline pressure. I also don't like being told what to do and always want to do the opposite. (I actually knew that before, so I should have known NaNo wouldn't work for me.) I know several Nano-ers this year who started writing in genres and styles they didn't usually write in.
Whatever your results, whether you made the word target or dropped out early, you can learn from the experience. Hooray for all those who tried, and good luck with your novels.