I had the feeling the end was rushed. Like the author stopped developing the story at some point and just gave it some end. So he went for a "hollywoodesque" end. I can live with that and since the follow up books seem to be bad, it's better then a crappy open end advertising part 2.
Haldeman is the somewhat unusual case for me where he wrote that one book which is solidly in my top SF list and he's never written anything else that I've found to be compelling or memorable.
This was my first but that is what I've heard from people whos opinion I trust also.
Most of the time I even read books good authors wrote in completely different genres just because they were good (Simmons for example). Even if I usually don't like the genre, the books are still good. On the bad side there is Neal Stephenson...I tried so hard to find the reason why so many like him...