Thanks for the information on HC-X900. It is a very good camera, and was among 4 top camcorders I was considering, among the Canon VIXIA HF G10, suggested by Bill.
I went ahead and got Sony HDR PJ710V, mostly because it was on sale at that time. So far I am pretty happy with the video quality, but still need a better solution for the audio. The built in microphone picks up sounds from everywhere, so if I am filming in a park, it will record sounds of cars on highways, airplanes etc. I tried ECM-HW2 Wireless Microphone, thinking if I move the microphone closer to the source of the sound (it records sounds being 300 feet away from the camera) it will solve the problem, but the mic is designed for picking up human voice, and wasn't that great for the nature sounds.
Currently I got the ECMHS1 gunshot mic, and it does a better job for my purposes, but still, I am thinking of recording sounds separately with a high quality gunshot mic close to the source, and then combining with the video.
A feature of the camera I really like it's the side projector! It is very handy when I want to quickly show my videos to friends at any place, without having a computer nearby.
One thing I didn't realize at the time of the posting is that the battery life was also an important factor, since I am recording for 2-3 hours in nature, without being able to recharge the batteries. The battery life of PJ710V is 110 min, as opposed to 75 min for HC-X900, and I still needed to get a spare battery not worry about running out.
Thanks for mentioning about the purple fringe, I'll keep an eye on the issue.
Thanks for your help.