1. How important is 1080 vs 720? I do not have the best eyesight.
It's appears that you have a price point and based on this comment you would be fine with a 720p TV. Most people will have a difficult time trying to tell the difference unless they know what to look for.
2. Similar question on 600hz vs 120 hz? I do tend to notice dvd motion artifacts, but i have no intention to go 3d.
600hz vs 120hz both refer to two different technologies. In Plasmas it's sub-field drives, in terms of LCD or LED LCD Tv's its refresh rate. Based on the different technologies used Plasmas tend not produce motion artifacts per say.
Bottom line you are the end user, it's what looks good to you. Spend some looking through some reviews and take them with a grain of salt. Tv's are not perfect and there will always be something that you don't like.