I've only parked in lot G, but I've never had any problems parking there. Be aware that that parking in lots D & E cost $12 a day, where lot G & H are $8 a day. D & E are the monorail lots, but with all the problems it has.is having, if it's down you still have to take a bus to the terminal.
If you want to check the Newark airport (or any other in the US). Go to home.digitalcity.com/airports. This is the Airport Survival Guide with links to many airports official website.