has anyone lost 50+lbs on 1700cals

I've lost close to 70 pounds eating around 1700 -1900 calories, 40 of those in the year since I joined this site.

50 pounds in a year might be possible, but I think focusing on that sort of goal can sometimes be demotivating. I know I gave up on some weight loss attempts in the past because they weren't going quickly enough even though I was losing weight. Try not to get too caught up in thinking about the one year goal. Thing more about daily goals -- eating healthy and exercising -- and about developing habits that you can sustain long term. You might lose more slowly that way, but you'll probably be able to better keep it from coming back.

Depending on your height/weight/TDEE 1700 calories might be the right amount of calories for you, or it could be that you could eat less or more. Check out this post for some good advice on setting a calorie goal:

http://www.myfitnesspal.com/topics/show/654536-in-place-of-a-road-map-2-0-revised-7-2-12

In the past year, I've lost just over 50 lbs and I average over 2000 calories per day. It's not as fast as it could be and I actually only maintained for over 3 months (averaged almost 3000 calories a day during that time), but I'm very happy with where I'm at. I probably have at least another year to go, but I figure that as long as the scale's going in the right direction and I'm satisfied with what I'm eating, then that's good enough for me.

Your losses probably will slow down as you get closer and closer to goal, but one way to combat this would be to exercise and up the exercise over time and to strength train. You may notice a slow down at first, but you will be rewarded with results in the end.