If you do have two hours to kill, the view from the observatory is great - I could even see my home on the upper west side. Times Square and the major NY areas look amazing from up that high. However, I went with my family in November and it was downright freezing out there and after waiting so long we only stayed a few minutes. It's all about the experience though right? I recommend not going on a weekend (let alone a holiday weekend!) or at night and you have a good shot of getting up there in a short period of time.