Hi Grasshopper!
I personally don't believe in setting goals to coincide with certain dates, and I'll tell you why. Lets say you set your goal as 150 lbs on 6/1/08. So that date rolls around, and you weigh 155...most people think "I failed!" in that situation. I find that ridiculous, since that person has LOST 30 lbs...a great victory! So my goals tend to be more about staying on plan and doing my best.
As for whether 150 will be a good weight for you, again, I find it is hard to predict. Why not see how you feel when you get there, and adjust as needed?
Can't wait to hear more from you soon!