Agreed, Clear Sky out of the box is the most appallingly bug-ridden crock I've ever tried to play. I lost count of the number of time it crashed on me before I gave up and patched it. I thought the ending was a bit of an anti-climax and the original far better, but there are some good features I really like, such as the ability to have weapons and equipment repaired and upgraded throughout the game as well as buying new.
Mind you, for a tenner it's good value and it'll keep you occupied for a bit.
The original promised so much and delivered very little. It was good, as shooters go, but in the end it offered nothing new. The initial talk of completely open gameplay, no zoning, "see it and go there" terrain... failed miserably.