Try some lighting. Like any of these little camcorders, especially this one, the video is not its forte. There's a big difference between a professional video camera and a $300 flash recorder. I went out and bought one of those work light sets from Home Depot and lit up a couple of videos and it totally helped the camera. The way to find out if you need lighting is to go outside and make a video in daylight. The camera will become a different animal and the video will look really good.
Being an iMovie person too, YouTube has a different method of uploading and they highly recommend following their instructions or sometimes the video won't work. So there's some kind of translation thing going on (for me anyway). But if I were to shoot something in 1080, or even 720, and stay in that format, a four-minute video can take almost 3 hours to upload. If it doesn't take that long, then you're not uploading your highest resolution, yes?