I used to have the green charge, but I cancelled it after a year's time when the annual fee kicked in. I got a nice 10,000 MR point signup bonus but the card really didn't fit my lifestyle as I thought- didn't travel as much as I intended that year.
I think it's honestly meant for those who travel more than the average person (and whom use their frequent flier partners)- the best way to maximize MR points really is through transferring pts to airlines, etc. Otherwise you'll have to go the gift card route. Like many others here agree- the green charge isn't that exciting otherwise; just a flagship card for Amex.
If you spend a decent amount on the card it'll help offset the fee a bit, though there are other cards out there that you may find have a better value in terms of annual fee vs. 1:1 point transfers. I think I only kept is as long as I did because it helped fund a free trip to NYC for me last September.
Right now I'm rocking the Blue Sky (no AF, essentially 1.33% cashback card towards travel on all purchases) to see how it plays out. I'm not a heavy spender right now, so it's taking a bit of time to rack up some reward points; fortunately it doesn't have an annual fee.
The Blue Sky Preferred version is cool too if you can use the benefits: $75 AF, but you get $100 airline credit per year as a statement credit (whatever airline you choose), and double points on dining/hotel/car rentals. Effectively 2.66% cashback towards travel.
I think Michael put up a review of it here:http://creditcardforum.com/american-express/1053-american-express-blue-sky-just-another-gimmick.html
Sorry to sound like I'm pitching the card haha, but I think it's a cool deal if you're not bound to one specific airline/hotel/etc.